For sometime IMC I've been doing something similar - the main church has no god and its clerics derive their power from the faithful. As a rule of thumb, it takes 20 or so parishioners per the square of the cleric's level to provide the necessary support which is passed on via daily ritual like prayer sessions. Thus large urban churches can support several clerics while several smaller hamlets must join together to support even one.
This keeps the clerics interested in what is happening "back home" as without their support the cleric is in danger of losing his power. To this end trophies and epistles are reguraly sent back, campaign stop like trips made, deeds are dedicated - all great plot hooks.