Here's how I would change the Kerbol system (Bold is new objects, Italics is moons, Underline and Italics is submoons):
In general: Stock EVE and scatterer, colliders for surface scatter, caves, new skybox with mostly black and few stars.
Kerbol: I would lower Kerbol's radius to a more realistic value, while increasing it's gravity in order to keep it's mass the same, as well as renaming it to Kerbol.
Ablate: 360 kilometers in radius, tidally locked. The side facing Kerbol would have an ocean of lava, while the side facing away would have a massive ice cap. The lava side would have a thin atmosphere of volcanic gas, while the frozen side would have no atmosphere at all. Surface gravity would be 0.45 g, and atmospheric pressure at sea level would be 0.02 atm.
Moho: Not much changed, but the Mohole would be more smooth, and be surrounded by a large network of caves.
Spud: 9 kilometers in radius, made of pure iridium, mostly smooth with few craters, in eccentric orbit of Moho taking it from as close as 1,000 kilometers to near the edge of Moho's sphere of influence. Surface gravity of 0.1 g.
Eve: Size increased to 800 kilometers, gravity decreased to 1.4 g. Atmosphere pressure would be 50 atmospheres at sea level, and the oceans would be made of liquid gallium, giving them a silver color. Sea level would be lowered to turn the oceans into large lakes. Atmosphere would be filled with dark purple clouds stretching from sea level to 30 kilometers up, meaning that the entire planet would be almost completely dark. Atmosphere would be 65 kilometers high.
Faz: 75 kilometers in radius, 0.06 g of gravity, visually the same as the old moon of Eve with massive crystals that was originally going to be in 0.17 but was scrapped in development.
Gilly: Same as stock in appearance, now orbits Kerbol with periapsis near Eve and apoapsis near Kerbin.
Kerbin: Mostly unchanged, better/more realistic terrain textures, colliders for surface scatter, which would be on every planet, as well as stock EVE and scatterer. Biomes would be redone, with forests looking like real forests and trees being crowded together everywhere, while deserts would have cacti scattered around, but being mostly empty other than rocks. Caves and deep sea trenches should also be added.
Mun: More interesting terrain, more contrast between light and dark on the surface. Size reduced to 170 kilometers
Pok: 23 kilometers in radius, lots of small craters, orbits Kerbin in eccentric orbit from about 45,000 kilometers to to about 80,000 kilometers.
Suk: 800 meters in radius, rocks everywhere.
Duna: More varied terrain, small lakes near equator.
Ike: Better terrain, otherwise unchanged
Magic Boulder: 700 meters in radius, covered in green streaks like the original boulder, has large network of caves nearly reaching to center, with monolith located inside. Gravity would be 0.005 g. Same orbit as original magic boulder.
Dres: More varied Terrain, Dres canyon extended to be nearly as long as Dres is wide, with smaller canyons branching off, and with large cave systems in it's walls. Rest of the planet would have more detailed terrain. Radius of 90 kilometers, surface gravity of 0.05 g, actual rings at dresteroid belt.
Veelo: Equatorial radius of 77 kilometers, polar radius of 41 km. Very light in color, with craters scattered across surface. Surface gravity of 0.03 g.
Thralt: Radius of 49 kilometers, same colors as stock Mun, crater scattered around. Large mountain 15 km tall covering half of planet. Gravity is 0.03 g.
Ferros: Radius of 35 km, made almost completely of iron, surface gravity of 0.07 g. Planet is almost devoid of craters except for one massive crater covering roughly an eighth of the planet's surface. Lot's of steep mountains and cliffs.
Yarovsk: 700 km in radius, covered in rusted copper, similar to the planet Kuprus from Extrasolar. Has atmosphere 60 kilometers high with pressure of 2 atmospheres. Planet covered entirely in mountain ranges, with massive cave systems everywhere. Surface gravity of 1.2 g.
Kamo: 224 kilometers in radius, heavily crated, very dark in color, making it almost indistinguishable from space. Surface gravity of 0.25 g.
Jool: 6500 kilometers in radius, now yellow with small swirls of green where algae live. Atmosphere 400 kilometers high and gravity of 2.5 g.
Melth: 100 km on short axis, 150 km at longest. Red in color, with gravity of 0.05 g.
Laythe: Oceans replaced with 5 or 6 large lakes, with moss and lichens growing on the coast. Large canyon systems would cross the planet. There would be lot's of volcanic activity.
Crast: 400 kilometers in radius, covered in craters. Otherwise not much. Surface gravity of 0.5 g, in binary system with Permios.
Permios: radius of 400 km, planet covered in deserts except for ice caps. Large dried out oceans cover the surface. Surface gravity of 0.5 g, and atmosphere 50 km thick with surface pressure of 0.6 atmospheres and oxygen.
Tylo: Completely redone, now a massive ice moon 1,500 kilometers across. covered in hills and cracks in the ice with craters scattered far apart on the surface. Thin atmosphere 40 kilometers thick with surface pressure of 0.3 atm and surface gravity of 1.8 g
Vall: Radius of 215 km, surface gravity of 0.12 g. Mostly the same as stock when viewed from space, with better textures, but with subsurface ocean and lots of caves below surface.
Bop: Mostly unchanged from stock, better textures.
Pol: Mostly unchanged from stock, better textures
Gron: 30 km in radius, green in color, otherwise normal, besides retrograde orbit. 0.01 g of gravity.
Bluv: 9000 km in radius, blue, gravity of 2 g. Same atmosphere height as Jool. Massive ring system.
Tildus: 1500 meters in radius, gravity of 0.005 g. Large cracks in surface and caves which go through the planet.
Daleth: 150 kilometers in radius, has one giant crater on surface like on Mimas in real life. Has lots of smaller craters and a surface gravity of 0.03 g
Minmus: 80 km in radius, atmosphere 20 km high with pressure of 0.05 atm. Appearance mostly same as stock, but with less deformity. Gravity of 0.015 g. Has subsurface ocean.
Telto: 530 km in radius, atmosphere 120 kilometers high with surface pressure of 3 atm. Kilometer-deep lakes of liquid methane on surface, gravity of 0.3 g. Basically Titan.
Rhys: 320 km in radius, has rings and is covered in ice, with craters. Gravity of 0.09 g.
Intra: 6 km in radius, shepard moon for rings of Rhys. Looks like a hamburger, gravity of 0.0007 g.
Outra: 8 km in radius, shepard moon for rings of Rhys. Covered in deep fissures, gravity of 0.0009 g.
Jall: 180 km in radius, half dark grey, half white. Has equatorial ridge and lat's of caves and craters. Gravity of 0.035 g.
Hype: 50 x 40 x 30 km in radius along each axis, looks like a deformed sponge. Gravity of 0.008 g.
Phil: 26 km in radius, orbits in an eccentric retrograde orbit around Bluv. Gravity of 0.004 g.
Eckel: 2000 km in radius, ice giant. Atmosphere 200 km thick, gravity of 0.7 g. Yellow with a red north pole.
Thol: 280 km in radius, half of planet covered in tholins. Gravity of 0.06 g.
Oksis: 550 km in radius, crust made of ice with oceans of liquid oxygen. Atmosphere is 85 km high, pressure of 0.9 atm. Gravity of 0.4 g.
Zilly: 68 km in radius, normal outer solar system moon. Gravity of 0.01 g.
Poseidon: 2400 km in radius, atmosphere 300 km thick. Basically Neptune when it had the Great Dark Spot. Gravity of 1 g.
Pro: 41 km in radius, dark in color. Gravity of 0.0075 g.
Teltonus: 160 km in radius, large amounts of cryovolcanic activity. Lot's of caves and mountains on surface, orbits retrograde. Gravity of 0.05 g.
Nelson: 33 km in radius, bright in color, eccentric orbit around Poseidon. Gravity of 0.00675 g.
Uraut: 3500 km in radius, looks like Uranus, atmosphere 300 km thick, 0.95 g. Has giant floating chunks of diamonds in atmosphere. Spins retrograde, and all of it's moons orbit retrograde.
Crakol: 130 km in radius, covered in deep canyons and has cliffs up to 15 km tall. Has deep caves stretching more than 10 km below surface. Gravity of 0.02 g.
Mermos: 200 km in radius, pink in color. Gravity of 0.04 g.
Umbara: 214 km in radius, very dark grey in color, covered in tall rock spires up to 100 meters high, with few craters. Gravity of 0.045 g.
Teltia: 300 km in radius, light reddish gray in color. Gravity of 0.085 g.
Ubor: 265 km in radius, medium-dark gray in color. Has lots of caves and craters. Gravity of 0.055 g.
Cucumber: 32 km in radius, gray, shaped like a cucumber. Only one of Uraut's moons that orbits prograde. Gravity of 0.007 g.
Eeloo: Retextured to look like Pluto, atmosphere 100 km high with pressure of 0.05 atm, 0.06 g of Gravity.
Karn: Basically kerbalised Charon, 90 km in radius with gravity of 0.0175 g.
Hauseo: Equatorial radius of 170 kilometers, polar radius of 60 kilometers. Gray with patches of tholins, has rings. Gravity of 0.03 g.
Hili: Same size as Outra, covered in bright ice.
Matka: 270 km in radius, oceans of water and land covered in Iron Oxide, making it and it's atmosphere red. No oxygen, thick atmosphere 90 km thick with pressure of 20 atm and filled with greenhouse gases. Ocean is over 15 km deep and has underwater caves. Gravity of 0.275 g.
Trius: 100 km in radius, northern third of planet is dark gray, southern third is covered in tholins, everywhere else is light gray. Gravity of 0.08 g
Ern: 230 km in radius, white in color and covered with deep canyons. Atmosphere 100 km high with pressure of 0.05 atm, 0.07 g of Gravity.
Roja: 49 km in radius, bright red in color, covered in small craters. Gravity of 0.009 g.
Selp: 180 km in radius, red in color from tholins. Gravity of 0.04 g. Has eccentric orbit around Kerbol, similar to Sedna.
Ploon: 1750 kilometers in radius, has large ice caps and oceans of liquid nitrogen. Atmosphere 90 km thick with pressure of 1.5 atm. Gravity of 2.5 g.
Clif: 270 km in radius, has large cliffs, made of ice. Gravity of 0.06 g.
Dot: 30 km in radius, normal outer solar system moon. Gravity of 0.008 g.
Rouge: 13000 km in radius, dark red in color. Atmosphere 550 km thick. Gravity of 4.5 g, rouge planet. Massive ring system.
Midnight: 430 km in radius, covered in craters, with limited cryovolcanic activity. Gravity of 0.2 g.
Hydrosos: 600 kilometers in radius, oceans of liquid hydrogen. Atmosphere 100 km high with pressure of 0.5 atmospheres. Gravity of 0.5 g.
Shel: 28 km in radius, dark red in color from tholins, shaped like walnut. Gravity of 0.008 g.
Igov: 7 km in radius, brown in color. Has mysterious igloo shaped formations and caves all over surface. Gravity of 0.0008 g.