@Jake: Yo, Guts can go kill some different stuff now; the scene's changed a bit, so there's stuff to react to.
@Lmpkio: Okay, lemme just... Stop you right there a moment and evaluate what you're proposing.
A kaiju gijinka is just... Asking for trouble, imho, ESPECIALLY one of something like Godzilla. I'm not allowing anything that has a semblance of nuclear radiation in, because that will SERIOUSLY not end well. I mean... I'd shoot down any suggestion for, say, Utsuho down, for example, because NUCLEAR RADIATION NEVER ENDS WELL. Also, I'm not fond of giant monster battles because of the fact that, unless they're primed correctly, they tend to marginalize characters. That's not good. Pseudo-invulnerability's also really iffy, imo; if the character is able to regen faster than the enemy can damage them, then it's basically an instawin... Which means that all enemies they fight are either mooks or have to pass that damage threshold. And I don't really like spiking difficulty because of one character.
I have zero clue who/what 'Kawrou' is, so... I'll inquire there.
Cloud... No problems with him, at least. I think.
I don't wanna allow Saitama in any form, nerfed or not, because then his identity disappears if you remove the 'one-punch' aspect of it all. No, really; I want characters to be able to retain their core identity without making them too weak, or else they're not themselves anymore and it becomes kinda disappointing.
Genos... Well, the weird thing about OPM is that Genos is used to frame characters as powerful, so the anticlimax of Saitama doing his thing is driven home. He's obviously damn strong otherwise, though; given what we can see out of the manga and the anime, he's got stupid amounts of firepower, strength, and speed that could possibly trivialize a lot of stuff. This one's a tossup, honestly; it depends on what he has the capability to do at the end of the day. Genos straight out of the series, though? Given the current strength threshold of the characters, I'm gonna have to shoot that down right now.