aw man i hope he fuses with it permanently. WOULD BE BADASS.U never know Lol, but I doubt that incursio will kill him it looks like it is fusing with him so there might come a time where Tatsumi has to be put down. He did tell incursio that it could have whatever it wants it. That is worse case scenario though.
I would also worry about Akame's trump card though. A Teigu that deadly which even someone of Akame's skill level can't bring out will be dangerous
and yea they showed her trump in the anime. idk if he'd change it, if he doesn't it was sick. won't spoil it for you.