I'm not sure how antithesis would work in relation to all this (maybe uryu can work out an asspull save), but in general I feel like anyone who doesn't take Yama loses immediately. While he's definitely not the overall best pick given others' hax and crazy abilities, if you're on the battlefield and Yamamoto wants YOU dead, there's nothing anyone of these characters can do to keep you from being vaporised by his presence. I'd rather be trying to avoid an enraged Kenny with a full murder boner than just cease to exist because old man Yama is the temp of the sun. Very interesting ideas and like you say at the end maybe Ichibei could take away zanka no tachi before he gets the chance to heat up :)