I got this idea playing a little bit back.
Essentially, it’s an upgrade to the good memory perk. Instead of slowing it, the trait completely stops skill rust (or slows it down even more, either or).
I’m aware that there is an option for turning off skill-rust, which I do use, it’s personally not always my favorite thing to do, but I see the appeal in playing with it on. And this trait could let you have an in-game reason for not having skill-rust affect you while having it in your game.
Now, it could be a pricey starting trait, mutation, or both.
I think it’d fit in well with the Cephalopod (the most intelligent of the mutants, makes sense they’d have this) and Alpha (to go with boosted brainpower, perhaps?) mutation trees.
Anyway. Just a little thought I had earlier, decided to share it.