LOL actually I always found Rakkus' power pretty interesting. He's a shapeshifter, whose alternate form is literally a virus. Which then infects people and lets him rewrite their DNA in order to turn them into this monster form that he possesses and controls. People see him on panel as this reptilian creature and hear 'shapeshifter' and figure oh he's just got some kind of were-lizard, but nah, he's actually a were-retrovirus and the giant lizard monster is just what his virus form turns people into. Theoretically, if he could work with other mutants like Hope or Elixir to 'tailor' what his virus form does to other mutants, like, there's some pretty interesting things that could be done with him.
But yeah, other than Chrome, I'd also be down for more Unuscione for the family drama (especially with Jared and Adrian thrown in), or Scanner - who seems like she could fit in well with a lot of current team lineups and has worked well with X-Men in the past even when they were on opposite sides. I've also always liked Katu and Milan. Rem-Ram could be interesting to play off of Somnus, and Projector's power has the potential to make him a heavy hitter under the right writer.