One idea might be to tone down the requirements. I like the idea of your sources; that adds interesting flavour, and I've considered these ideas myself, but not yet implemented it. Let us know how it goes!
In response to an earlier post, I think that its not necessary to go through every spell in the phb and assign requirements initially; if you have some broad ideas how this system will work, you can probably assign on a case-by-case basis. After all, there's a good chance that 50% of the spells or more may never see light of day in a standard campaign. In fact, one idea might be, if you want to involve your players more, to have them suggest the spell requirements as they pick their spells.
I agree with earlier posts suggesting that it might be too much to have a price paid every time a spell is cast; could it be an alternative instead to have, much as clerics and paladins work now, that the caster simply act more or less in accordance with with their particular source's dogma? Perhaps they are required to make some sort of periodic devotion too.
Just a thought, too, which may or may not be that useful to consider; Some level of maturity is required in the game, but I also think, depending on your players, sometimes the folks just want to get together to roll some dice, kill some stuff, and take its treasure, which can be heaps of fun! Perhaps you are confident that moving your game in a particular direction with mechanics will improve the game for everyone, though maybe it wont.