In principle, you can create the model in any suitable program. Even creature models. You can easily create a hero with their own characteristics by exploring the properties. You can assign any model: a regular creature or hero, any skills, specializations, their names, images, and everything else. If you're interested, I can post instructions on how to do it.
Actually, what I want to do is this: In the original version of Heroes 5, Inferno had 2 skins for the hero, something like a male (the standard one that exists now) and a female (a succubus, like Biara). I want to bring that back. Let's say Daleb has a succubus skin instead of a bulky guy in a hockey mask.