I was wondering if Steve has considered at some point to split planets into objects which are made of several continents, each having (possibly) a different terrain. Hostiles races would be able to co-exist if not on the same continent, and reversely (somehow) conquering a planet would ask for the invasion of all continents. You could even have completely liquid 'continents', with a kind of blue navy present and defending it (well, that would be version 2 of the implementation perhaps).
I have read my share of books where planetary conquest is made with an initial beachhead, and then you need to push further to different environs.
Edit: OK, I have read all Steve posts since 8 months, with the exception of the new AAR! When is 2.0 coming out, I'm hyped and I think I'm done gorging myself with Rimworld
ps: are the cosmetic components in btw? Please say yes, can't wait to design superfluous infirmaries, brigs and armories.