Heroes of Might & Magic III: Horn of the Abyss

similar to the fifth installment of Heroes of Might and Magic?.. but is it necessary?

It's not necessary. And I can tell you why. It seems they wanted to create a mod that is as close as possible to the original Heroes of Might and Magic III :)
And would there even be enough space for it?

And another question. Will the beta version include a second branch of creatures?