EDIT: Split from hereWas thinking of about race developement and reading some race ideas in "Post your races here".
Just creating a "oh i think this type of crystals race should be cool... and they will have good bioharvesting! and good ecology! because they are stones and need organic food! and because..." does not feels right, if you wish to have all races be playable and balanced, if you wish them to be logical. Ofcourse there can not be ideal balance in such a huge game, but here is idea:
First thing to start with is not placing a ready races,
i suppose it could be right to begin from creating different colonisation possibility. What i mean ? For example, type A has better population grows on small(low grtavity) terran planets, type B on medium desert planets, type C on gas giants et.c.
After that you can observe how population and colonisation differs, and it becames possibleto correct this information by changing how often some kinds of plannets appear in galaxy. This is only real thing i see possible at theese stage of game development.
+ environmental difference of planets required
The next step should come with trade and random resources on planet (for example 2 desert planets can differ in ammount of minerals they have, and while averange bioharvesting is low it still can differ) only then it becames possible to determine what types has strong bioharvesting and mining ability and can sell food and minerals, and who prefers to buy their food. Who mines for themself and who uses foreing resourses to maintain full power of their production capability. Huge space for subtypes. Or for interface where players can adjust their subtype as they want.
And the third step comes with good diplomacy mechanics. Here will matter how your spices looks like and how other spices look at you. Here your story is really matters: abilities do not come from story (ofcourse if your race is not someone's genetic engineering project), they come from evolution, from conditions on the planet and it's resources.
When all of this finished it is time to make unique mechanics for races (like silicoids eat only minerals et.c.) as final step
the other major thing: the story about evil as satan guys must be avoidable, so you can play his cyberinsects not just as xenophobic "i-kill-all-i-see" (as i love to play), but also as peacefull cyberisects.
P.S. sorry for my bad english (not my main language at all)