Apologies in advance, this is not meant as a brag post. Today I got a 6 star 4-5 rank up gem crystal and unfortunately (for me at least) landed on Mutant. Mutant used to be my favorite class, but now it's probably my least favorite. I currently only have 2 mutants at r4, Apoc and Weapon X. I do also have an R3-R4 mutant gem, so I could take up any of these folks in the screenshot below to 5/65. I don't run the "ouchie" masteries and don't really have an intention to do so in the foreseeable future. I'm currently in a solo alliance, so prestige shouldn't matter, but as you can see by my R4 rank up choices, I did take prestige into account in case I switch to a different alliance in the future.
I should mention that I'm not particularly good at playing Kitty (I'm not the best interceptor).
Currently, the mutants I have that are max sig are: Weapon X, Kitty, Professor X, Stryfe, Omega Red, Archangel, and Domino, if that matters to your suggestions.
Taking a look at my mutant options, and my R4s as a whole, I'd love to hear suggestions on who I should take to 5/65. Thanks!
Here are my current R3 Mutants:

And here are my current R4s, including 2 Mutants:
