Maybe someone can offer some advice.

It's a bit more complicated here; it's easier to say what isn't working. I reworked each mod myself, and after 1000 attempts, everything finally worked. There are only 3 issues left to resolve. As for the mods, NHF, NAF, and the visuals, I created and added the hero models myself, and partially used elements from Heroes 5.5.
But 5.5 doesn't have an impact, nor does NAF (I had the same issue without them). I might have made a mistake when assigning the models, which could cause the game to freeze when the surrender button is pressed for one of the heroes, but I don't see it happening, and honestly, I don't know what in the code would cause that.
As for why the hero isn't visible, it's possible that something is conflicting, as I combined things that are supposedly incompatible. But even if it were modified models, standard models also disappear.