Sorry to say it, but the need to find a friendly priest to maintain your magic has always been there in RQ. Why did you think that there were four Orlanthi rune levels hanging out in Trilus?
There's no point in making hard and fast game mechanics for it, but if you are a divine cultists and leave your community, at some point you need to either make a new community or join a new community. That can be as easy or as hard as the Narrator wants to make it. In my own game, it would at least require the character visiting the temple, offering some sort of gift or pledge of loyalty to the priests, and spending a Hero Point.
As for the lack of universal cult structure for Orlanth (and plenty of other cults), that's not new. That's straight out of Cults of Prax.
Jeff
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