Using the Tat's spell system from Spirit Lake is exactly what I was doing with Patterns of an Age. It works pretty well for a lot of things, but some weaves are just going to be difficult to put into that context... but that's fine really.
Tat's system is awesome, but unless you've got the time (I turned out not to), I'd stick with regular FS3 and just some simple guidelines/weapons/skills to mimic channeling like some of the other magic based games have (the nazi punching one I can't remember the name of, for example)