I'd like the game to be reasonably playable with any race, class combos I choose so that I feel like a masochist for playing a gnome bard or something. Though at the same time I'd like the game to have major challenges perhaps through optional challenges, alternative story routes or just an insane difficulty level. Being able to replay the game again with your maxed out character against much harder enemies could create that challenge too.
Basically, easy for everyone with an optional challenge for the hardcore.