I don't know about casting, but if they do a TV series, I think I'd want mostly new characters. The show could be about the New World Coven, or the war told from the perspective of the lycans or something.
Hi guys, I think Underworld would be an amazing series if they start from the begining. I would love to see a show that starts with the 3 covens as they battle for power and how it then proceeds to the rule of one. IE 2 sleep as 1 rules the three covens. You could use the lycans as bit players at this time, show how their rebellion is just starting. But the real batttle is the politics and waring between the covens. For the second season then bring in the Lycans and the turning of Selene and her crusade against the Lycans. Then in the 3rd or 4th season bring humans into it, for example you have the Lycans and the Covens and a human government factions. So at this point the humans are aware of the immortals and are trying to form a treaty of somekind. Then bring in a human protaginist, who meets Selene and is dragged into the story, you could do this by throwing him into the scene where Selene meets Alexander, then during the attack by Marcus he tastes Aalexanders blood. So he becomes a valuable asset as he hols the bloodlien of the most ancient vampire. You could then have this human as trophy that the vampires, Lycans and humans were after. The ideas are out there, it would be an amazing TV show. The sooner they make it the better. Fingers crossed.