If you wan't to prevent temples being used as banks, then tax gold withdrawn from templetreasurys rather than the treasurys themselves. Either by the local lord or the temple itself. If the religion gets to keep 250 of the 500 gold I have stored in a temple when I want to withdraw it I can guarantee that the days of temples being used as banks will be over. Without making funding temples harder...
And thus completely kill any possibility of religious crusades, which often rely on temple treasuries to fund the crusaders.
