The RNG that is mutations is frustrating as it is rewarding. The loss of deterioration can be coupled with the loss of that nifty quick trait. Thus, there should be special mutation locking drugs that prevent a present trait from being affected by both purifiers and mutagens, similar to how Darkest Dungeon locks quirks. On one hand, you don’t lose your traits. On the other, you can’t upgrade them either.
To balance this, these locks should be more expensive than purifiers and not protect against outside sources of mutation (ex. yuggs and radiation). Maybe these locks could act like smart purifiers, locking multiple traits in, but that would screw over some survivors (ex. locking in deterioration).
The problem (?) is with balance: late game survivors will be unstoppable genetic killing machines. In fact, Chimera would be even better due to keeping all the cool mutations it has without Genetic Chaos losing them.