New characters would be a great idea

New characters as in... ?

Are we talking new characters in the global story, new characters in a particular game, new characters as in new races?

You're being rather vague.

What? i am not exactly sure what you mean by new characters

New characters as in race at 2 or 3different from the original races

Ok, i see where you're comming from now.

The problem i see with that is, if you're not careful things become impossible to ballance, and each race loses uniqueness. For instance... aside from a little resistance to cold, there isn't all that much to separate the Snow Elves from the High Elves. Or the Tropical Elves from the Wood Elves. And if you start pulling in Akaviri, well... that creates all sorts of messes, what with vampiric, form-shifting snake people...

I think a far better choice would be to create cultural divisions amongst already established races. Ashland vs Great House for the Dark Elves, Colovian vs Nybanese for the Imperials etc. It creates variety, while maintaining the already established themes, and wouldn't be as hard to balance.