Yes, Alan is right – Heroes with 4 factions will be more similar to Disciples, and having too many factions wouldn't work, simply because I haven't seen such a large number of factions in any game where it's still interesting and they aren't just clones of each other... it's just not possible. Let the expansion come out, and then maybe a couple more factions can be added, but after that, it's time to stop – if they release more expansions, it should only be to further develop the existing factions or simply improve the game.