/**disclaimer: not appropriate for running a business*/
tell the fuckers that how they're currently playing it, there are 3 options:
have it sound shit
have it so it might as well be programmed
fuck off and practice/write some music they can actually play!
/**on topic*/
I don't think anyone will notice if the consecutive uninterrupted cymbal hits in a piece are a little bit late if you're only slowing by a couple of BPM. Hell, it might even add a cool sorta swing in slower sections as long as you don't let it go too far