I actually have been working on this lately. The actual process of changing out mutations is done, but no real mutations have been implemented, only the pre-existing vanilla traits. So I test played for an hour or so and it was quite cool. There is, as of yet, no system in place for getting new traits/mutations, but you start with access to every trait in the game already available. You gain mutagens over time and expend them to change your active mutations. I would use Fast Shot when I was sniping to get quicker shots and then switch over to Trigger Discipline for the better accuracy when using low accuracy weapons.
I would toggle Good Natured on and off as I entered and left town to boost non-combat skills a bit.
I toggle Early Bird and Claustrophobia on and off at appropriate times to gain their benefits without their drawbacks. Same with hoarder. Note that I made everything REALLY cheap at the moment, so gaming the system as hard as I just described should be impossible without investing in lots of perks and upgrades.
And honestly, none of that makes any sense because those are personality traits and, while personality and genetics are linked, does not make sense in this context. In the future I will try to add new traits that are physical, like Four Eyes, and remove the personality traits from the list of available mutations. For now, though, it is just cool to see the system working.
