Something like this has come up before, most recently here:

http://forums.carrionfields.com/dc/dcboard.php?az=show_mesg&forum=8&topic_id=739&mesg_id=766&page=

I wanted to test something like that out with the Scarabites after they went from cabal back to religion, but I have yet to see a shaman. So now all followers get some supplications to choose from instead. But I imagine it would be more advantageous to have one or two supplications for non-priest followers and an additional 1-2 for priests (either for shamans or healers or both).