#1: I wish all planets had three stats - size, "type", and "moon". Size would represent the starting development limits (or size) of the planet (possibly to be increased by certain techs), "Type" would represent the techs necessary to colonize the planet (radiated, lava, arctic, etc), "moon" would indicate presence or absence of moon (to be developed via certain techs).
#2: Ability to create specific techs that would "improve" the "type" rating of the planet.
#3: Ability to create specific techs that would allow moonbases of various function (bonuses to home planet).
#4: Wish we had a new development module for ships (constructors?) that could create artificial planets (perhaps one per star?)(assuming proper tech was researched).
#5: Wish all races had an "ability" that determined what types of planets they could colonize at the start of the game (without additional tech).