As far in on handbuff as I felt I could go. Kitty Pryde is a cool include because I can jump her back to catch a nakia buff if need be. A couple anti synergies with bast + black panther/aero but aero is an amazing card and black panther is good with each of the other buff cards. Just a theory craft but I've seen hand-buffy builds with brood work in the past.
Edit: Alright so Aero and shuri are out. Aero is less playable in all decks and shuri is specifically less good in this deck because her condition really hurts us. In their place I'm on wong to go all in on black panther zola but also nakia then forge on 5 is a lot of power to something turn 6. In that same vein I'm playing mysterio because I can end up turning it into effectively a big doctor doom (I assume only nakia, okoye, and bast would work great with it though) I could end up cutting kitty now that she works differently but I'm not sure what better cards I have for that slot besides maybe just a nightcrawler since it can be really flexible with a buff? I'll have to do some testing first.
Edit2: Decided to swap kitty out for nightcrawler as a flexible 1 drop that is decent to buff. You just have to spend your energy efficiently a lot of the time with this deck so it's hard to fit in kitty turns.