I know that the Kerbol system isn't the most realistic (1 gas giant, 2 moons for Kerbin) system in the world, but having only 3 main moons seems a bit off for a towering cloud that Jool is. I just want to make the game feel more interesting.
There's a wide open space between Tylo and Bop that constantly makes me irritated. I always feel that the potential for a moon to be there is just too high for there not to be one. It doesn't have to be either flat or lumpy like the other moons; real life Callisto is cratered and rigid and interesting! It would be so fun to see the protector of the inner moons watching silently over the Joolian system!
That's all that I have to say!