I would like to see the planets having a tilt. To make landing more of a challenge, imagine Val rotating retrograde like Venus does, or a pole close to where the equator is on some planets like Uranus's near 90 degree tilt. Also one of the moon of Jool rotating retrograde around it, maybe bop since it could be a captured asteroid. As for science I would like to see a medical exam when the kerbal returns from orbit, perhaps some tweaks required for further safe exploration. For example you do a suborbital or single orbit flight when you start the game, collect science about the reaction of the kerbal's body and then use that research to create a safer capsule for longer duration flights. Perhaps a resource like elements that can be recovered to create atomic fuels, so say two trips to Duna and back allows you to make enough fuel to go to Dres or Mojo one way on a stock atomic engine. The basic idea being collect resources, spend money and get a fuel that makes the ISP double, repeat this till you get to Pol. Finally I will ask for this every update till I see it, a ringed planet.