Hi, is it possible to turn off mercenary component in Rhye's and Fall RAND mod?

Nope. Sorry. :(

you should comment in CvRFCEventHandler.py, inside onBeginGameTurn and onBeginPlayerTurn, all the mercenary stuff. It will be still shown on the interface but it won't work

Well I was gonna say not without diving into the Python code, but yeah that works too.