Now, who said the mixer had to go on the desk? Check this: https://reverb.com/item/56181294-alesis-multimix-12r-rackmount-12-channel-mixer

Mine's immediately behind me...and it's the dedicated mixer for the lab gear setup. The nice thing about that sort of thing is that you can get a rack case, put this in, put MORE stuff in with it, and now you've got a rack for FX and mixing. Just put it on a stand (like a chair, even) next to you, and save the desk space.