I thought I’d take a look at flight. It’s a pretty common ability, even in real life. It should be possible for creatures to fly.
Fairly close again, I think. 75% of the creatures can pay for their flight out of the slots available at their tier, and it’s not that hard to come up with supplementary talents to fill out where they don’t quite fit. I can easily account for a bit better than 90% of the flying monsters from the RSRD.
As you might expect, outsiders and creatures with the Air or Incorporeal subtypes are the most problematic… but still reconcilable.