I too find it astounding there's a whole group of player who want to play clerics. I remember there was a time when this would have been a situation that damn near most D&D players would find inconceivable. It used to be cleric was the class foisted off upon the newbie, 'cause no one else wanted to play it.
Still, there's no major problems here. If, as you say, the players DO engage in roll-playing and not just mindless munchkinsim, then let them enjoy their holy smackdowns. If they're all part of allied faith, maybe set up a situation where a powerful god of evil is waging war against the good faiths. Give them a crusade to fight. The bad guys will probably have lots of evil clerics to foil them.
Don't forget church hierarchies, too. Most lawful and a good number of neutral churches will have superiors the clerics are expected to obey. Only chaotic faiths will tent to let the priest do whatever they want. Of course, if the heirarchty is corrupt, and the priest is faithful, that could offer some good role-playing opportunities. Especially if the god in question is refusing to grant spells to the heirarchy, but giving them to the PC cleric.
As for hirelings, enforce some role-playing flavor here. Tell the players that they can only hire NPCs who are faithful followers of the church. This may very well cut down on rogues and wizards, if those classes tend to be rather impious.