Tf2 in guilty gear could be a perfect cross over.

For both of these games being different in both art and game play, the tf2 characters would fit into strive very well. I think their arsenals would lead to unique and fun play styles. I think out of all the mercenaries the pyro would fit in the most, with his jetpack giving his air mobility more flavor and his air blast could be like pots flick but sending the projectiles in a random direction, and he could have his own ammo counter that depletes when he uses his flamethrower , and he could use his flairs as projectiles that goes full screen(the flair gun he uses would be the scorch shot).