I was figuring they'd be customs.
I already had an idea for a guy that only has 5 magic circuits, and specializes in a self-developed variant of Gandr Shot called Gandr Snipe(Sorta like the Fin Shot, but only works with Hunter's Mark.), as well as tracking spell called Hunter's Mark, which works to improve/enable Gandr Snipe by increasing the casting range/enabling it to be cast.
See, there's 4 circuits in one of his arms, and another one in the corresponding eye.
Of course, that's about all he can do, because he never had formal training, much like a certain other Magic-user...
But hey, when all you have is a hammer, eh?