the idea of a level cap is horrendous to me
and i like the idea that stats are mostly connected to bodyparts and skill is connected to experience like it is now. maybe have bodyparts get better after some time so that people that refuse to mutate can improve their stats a little? like having a well trained muscly arm instead of a wimpy arm. could also give a slight debuff to a newly acquired bodypart when you are still getting used to it, it would probably take some time to learn all the things you would like to do with the tentacles you just acquired
a lvl cap means you cant roam the world forever and while that is not something everyone will want to do for every game it would be removing an option