[Qhaysh]

Another option that occurred to me was to simply clump two relative skill levels to one attribute and have the magus roll against that.

So let's go back to Blastius in the first example. Let's say he has an IQ of 14. Since all skills are VH, he has Creo 14/+0 [8] and Ignem 18/+4 [24]. If he were to cast that same spell upthread, his base Creo Ignem roll would be 18 (IQ 14, plus 0 from Creo and +4 from Ignem); further modified by the spell's energy cost of 42 (-5), for an effective skill of 13.

But this just sounds weird to me, so I'd gladly welcome another way of dealing with the whole "one feat, two skills" thing