And thus completely kill any possibility of religious crusades, which often rely on temple treasuries to fund the crusaders.
I actually liked the idea you quoted, and have two answers for you:
1) Is banking not the issue? Thus, financing religious crusades avoiding Banks?
2) If the Lord of the region your crusaders draw from is a believer, then you can still do it. He will simply collect the taxes and deposit them in the temple again, for the crusaders to draw on. It would even create some nice possibilities of conflict, with the Lord sending back all, part or none of the money deposited. Corrupt local lords profiting on devout foreigners? Crusaders having things more difficult by avoiding the normal legal banking system? All very good to me. What do you think about it?
Summing it up, you would have no tax in depositing into Temples and Guilds, but you would have one on anything you draw from them. It would solve the Banking issues, not contributing to the temple/guild maintenance ones.
Want to fund a crusade? Be ready to entrust and severely empower the local lords you will depend on. If you do not, you are just circumventing the existing banking limitations unpunished.
