i was actually going to text you about this earlier, but life got in the way. Another way to do this would be to build a few custom spells for him using the "Powers" in the BGB.
It's a poorly-guarded secret that the demon abilities in SB4, which were the prelude to those in Elric!, were created by making up little clusters of powers/disads using the Superworld rules. The "CV" cost of those powers is the end result of building them with the Superworld system.
So, one way to do it would to be give Gary a budget of points to spend, and just let him make up his own powers using those rules.
Failing that, maybe look at "Deep Magic" in AS?
Please note I do not actually work for Chaosium; I just do the occasional freelance editing work for them.