GURPS Earthdawn

[Kalzazz]

I'd put some kind of reflexive, reduced time with loads of penalties on the modular ability as an option, to reflect 'you can, if you are suitably desperate or dumb, save a second or so by casting raw'

I wouldn't worry to much about it though . . . casting raw magic is in my experience used somewhere between never and very rarely

Among other things, the times when you are in dire straits enough to contemplate it are usually in corrupt areas where its suicide. In the more safe areas, you usually aren't desperate enough to try it