King because he's king, Zombieman because his regen would offer a power that they don't have, and he'd also probably be a help to batman, and maybe flashy flash even tho he'd not even be the fastest one on the team lmao. Although actually, he would be the fastest if we go by the the dceu, which is actuallt within the 6-C and relativistic ranges, making him somewhat compatable with the verse.
Blast wouldn't be a part of the league but he'd probably be their ally, since he's already part of his space team
Metal knight is pretty ****** unhelpful, in fact he'd be a fitting superman villain or rival if anything lol. But he is one of the strongest non god tier heroes, and he is the most resourceful hero association member.
Tatsumaki is annoying and also is a child but she's strong enough and is a psychic, so maybe she could be a good pick.
if we go by the dceu then the only hero other than saitama left to be strong enough would be metal bat since he can become 6-A
of course, there's always the fact that garou is maybe gonna become a hero, but it's human garou who likely won't be receiving anything past 7-B since Saitama beat the monster out of him, so he wouldn't be a good pick either.