Adam Devine from Workaholics would make a good Murray replacement. Charlie Day would make a good Ray. Donald Glover maybe as the Egon? and a girl as Winston though I'm not sure who'd fit in that overall framework with the others(Amy Shumer?). Nick Offerman should be in charge of P.C.O.C. in the Walter Peck type role. I don't mean like doing impressions mind you, just that framework of like Venkman being the face, Ray the heart, Egon the brains etc.
Unfortunately, given that Dan is canadian and SNL alum, I'm not sure any of those guys would end up in the running and that's a damn shame.(i dont know if Dan even knows what Workaholics or Always Sunny are)