"Self sponsored" magic is a misnomer gained by trying to fit the type of spellcasting in question into Sponsored mechanics. "Self-sponsored" magic just represents a greater talent/skill/experience in a particular field that supercedes simple Specialization; it provides expanded ability in that field (primary, evothaum).
Kemmlerian necromancers, for instance, can't really do anything any "normal" necromancer couldn't. They're just better at it and can do it really fast (evothaum).
A stress track is an interesting thought, but I think that doesn't really fit with what "Self-sponsored" magic is; it's greater knowledge/skill applied to magic, and shouldn't be limited by how many times you've already done that kind of magic that day.
Taking Debt to Self-Sponsored magic is different. Some GMs allow, some don't; for me, it's conditional. Using the Kemmlerian example, I'd allow one or two "debt" points to be taken at any given time, and use aspects related to their necromancer for the compels (most likely a Lawbreaker aspect, given the type of magic we're talking about). Taking sponsor debt for Kemmlerian magic would drive you further towards using more of it to solve your problems, etc.