There's no reason this can't work as an IoP. That's a pretty perfect rules system to implement this. It is ALSO a Fate Point Farm in that it gives you an extra Fate Point every session. If it is essentially a massive crutch for using magic, there's no reason why a GM wouldn't let you spend a Fate Point to emulate the IoP for a scene. All that seems like a good way to have it work. This would stretch the IoP rules slightly only in two respects. One, you couldn't lone it out (by that's an easy agreement for everyone at the table to make). Two, an IoP like that is probably going to be worth something like 5 Refresh (3 Thaum, 3 Evoc, -1 Size). So as a temporary power one Fate Point might seem a bit light, but I don't think this is the case since that's actually most of the character tied up into that one item (and an item that just gives say Ritual, with all other powers part of the character, would only cost 1 FP). Hmm, as far as Temporary Powers like this go, I would say that if you lose an IoP that is a crutch like this, just paying the discount of the IoP in Fate Points makes sense to activate the power for a scene.
An aspect is another way to go, to about the same effect. Then again, you might be able to find a more interesting aspect instead -- I am not sure how much this one would come up.