Like regular rampant, I think there should be an option to start at T0 rather than T1 or T2 of Rampant Fixed. Not expecting this to be implemented at all, but it'd be cool to have considered at the very least.
Right now, Rampant Fixed starts the world with acid biters spawning which are a T1 class of biter, and it won't take long for T2 classes to start spawning. Regular Rampant starts you off against "Common" biters, I think it'd be nice to spawn worlds with only T0 common biters before you start seeing T1 class biters like Acid.
On the other biter types from the custom ones, is it being looked into making them have LV1-LV10 spawn types as well or will they simply remain as small/normal/big/behemoth types with only their AI being altered? I fully understand the mod recently updated so I'm not expecting fast implementation/consideration at all, I am simply opening the idea up and bringing my thoughts and concerns forward.