Well actually in Arx Fatalis you don't have to be a mage at all, the alternative of being a Thief for example is actually implemented like the Thief series..in other words you can finish the game with minimum killing and stealing/picklocking/sneaking. Most of the xp is based on "progressing the plot". I'd actually compare it more to Quest for Glory than the mass-killing Diablo/DD/Baldurs Gate type of RPGs.
The gesture system in Arx i'd say is fun, but it's hard to work with. There's no pause system and imagine drawing special runes when a monster is running at you. Their solution to it was memory slots to precast, but to me it led to a chore situation..you stop, pre-cast (on your own time) and then release when a battle occurs and repeat..so the actual battles were never as exciting as it could've been, even the simplest of spells can be hard to pull off in a hurry.
Either way, rightly implemented i think it can work in any game, in a 2D game, it can be like Black & White where the magician draws the patterns on the ground. So from DD viewpoint, you would go into casting mode and draw on the floor (still in 2d, no special thing required). Although the sheer amount of combat (Arx fatalis doesn't have alot of combat in comparison) make the system a bit tedious BUT if the most powerful of spells were to have such a system then it will rock. In other words, those power-word-kill type stuff that would kill things instantly etc...that will certainly increase the challenge.
