[size=10pt]Alrighty! [/size]
So I floated the threshold suggestion awhile back and as that seems to have been well received it’s about time I suggest something else.
Forks
As it stands with thresholds ((Correct me if I’m wrong)) you can fall into a category and be unable to purify certain post-threshold mutations. That’s great. I like it. Let’s take that idea and run with it.
Forks would be where certain mutations ((mostly post-threshold)) branch off into more than one possible path of in category progression. Similar to how head-bumps or rough skin could turn into any number of things, these would be either-or post-threshold mutations, locking you permanently out of the other choice.
Example : Spider mutagen as one would expect, let’s you weave webs, eventually letting you block LOS and give the ‘webbed’ debuff to anything walking through them. Oddly enough web weaver isn’t post threshold, but we’ll ignore that for now. In this scenario web-weaver is where you fork, having a chance to gain:
Stickier webs that trap anything walking through it like a bear trap/snare
or
Stronger webs that non-spider’s can’t walk through without some serious (S)mashing
And the key here is ‘or’. Ideally these forks would add a bit of in-category flavor to your mutants, making it unlikely for a player to wind up playing the same mutie twice–even within the same threshold.