Is there really that much use for collision detection?
As for wish list -
Something to show planetary orbits
And vessel trajectories at run time
Would be quite nice to have.
Would make planning trips and understanding what does this ship do when the trajectory is like that much easier.
Not to imagine the trajectory based on the output of some MFD, but to see it in game.
Someone unfamiliar with orbital mechanics would see that launching straight up will make your trajectory intersect the ground again, without need to grasp the meaning of orbit MFD.
Essentially, put orbit, transx, etc, MFD's out into the main rendering.
Another useful thing would be a velcro rockets visual editor.
Or just in-game editors to piece rockets together.
Seamless gameplay - ability to rewind and restart the game pronto, without need to exit and start it again to change scenario or try a launch again.
Or to edit your launcher.