I had been thinking about this game from the perspective of street mages, maybe it might be better to play with the concept of familiars to street mages.
The reason I've considered this is because I'm not really interested in developing a complex magic system for the game, except as a storytelling effect. Instead I'm thinking that there will be magi who act as conduits reaching from the human side to the mystic energies of the beyond...and there will be familiars who act as conduits from the beyond, reaching toward the mortal realm. Familiars form bonds to magi, each strengthening the link of the other in a symbiotic feedback loop.
This helps explain why the characters don't have money, just a limited number of tools and edges. Familiars don't need to improve with experience, but they may gain stronger influence over the world as they establish stronger relationships with the magi, the eternal constants, and other elements of the setting.
I'm not sure if this is a good direction to be heading, but it feels interesting.