The weak point is usually the engineer.
Having a system that minimizes the possible disasters is usually the solution.
When I had many gigs on big stages I had a radio clip-on feeding a multi-effect allowing me to give them a L+R and tell them "no eq, no effects no nothing".
Still some managed to do a mess, since I was giving them a line level, while they expected a mic (much lower).
A friend of mine (a very good engineer) once had to work with Chic Corea's Electric Band.
He hired the best gear in town, but when the soundcheck started, Weckl, Patitucci, Marienthal and Corea gave him a L+R each telling him "no eq, no effects, no nothing".
It reminds me of another pianist that sends pre-written articles to music journalists, but this is another story.
I'm intrigued about the pianist..!!