For the issue...You can use the 'Adaptation' part of the class description:
"Secret societies of Ur-Priests could exit for the express purpose of elevatating (or re-elevating) someone or something to godhood."
The someone or something could be the chaotic or evil deity worshipped. I guess it would work best with 're-elevating'. That should help you reconcile the two requirements.
Interesting. That could work perfectly. One member of the party is a Cleric of Orcus who, as I understand it, is not yet quite a god but only a demon prince on the path to ascension. So, that might work perfectly. Thanks Rich.