Why would hiking taxes make your knights angry? I can't imagine they would care. Also, i can think of a few ways break your guild financial system, without breaking any rules. Also, swearing to a maximum tax rate? Yeah, that's a bit overreaching.
Indeed: higher taxes means more gold for them. Guild taxes are based on region taxes, not lord's share.
I had started a Dwilight Banking Guild, though I don't recall the name, but I quickly came to realize that it could be so easily gamed that I never put any effort into developping it and let it die.
