The way it will be done in Tactica Online sounds pretty promising.
Game is set in an alternate Renaissance era. So, you get your alchemists, new technologies popping up, etc. Faction based on Da Vinci.
On the other side, the church still holds much clout. Go inquisitors!
And, of course, the magic-using heathens. BURN THE HERETIC!
Adding in the 3rd faction really makes it more appealing to me, in providing extra context. It also make magic more appealing at the same time, too. Playing heretics is more fun than playing every other mage in the gameworld.