DJs using controllers run into this a lot. Clubs Do not want to wast time on your setup unless your are headlining. You might have DJs before and after your set and with an external controller might replace a CDJ or turntable channel. Sometimes there is just no room for your controller. This is one reason I use software that can use a controller or time coded media. I use Traktor with Xponent and the time coded media if needed.
He should be ready for any situation. There are many other situations, setups for performers but I am sure that is not what your are talking about...
-Lars