Dan. Adding a better collision system isn't the MAJOR priority(i think), the major priority is correct ALL the bugs.
I made a list of the priorities :
1. Correct the Bugs - #1ST PRIORITY#
2. Adding Chalenges, Missions, More tutorials - #Would atract people unfamiliar with Simulators and/or with the space, Universe Sandbox, et cetera.#
3. Adding more things - #People want more things, like Spacecrafts, Satelites, Spacial Bases, some are even trying to add Ponies to UBOX2#
4 and last. Adding better grapphics - #Collisions, Stars Flares, Those things...#
I hope i didn't offend anyone, this is only a criticize.
Good luck to the UBOX2 developers, we are expecting a good game(also sorry for my bad english i'm from Brazil).