I am definitely going to do this myself and had considered (because I wanted both machines at a pleasant working height) attaching them to the opposite faces of the same base and then by some cunning method have this base swivel and then lock into position.
My back is rubbish and I just couldn't get my head around having the bed of the thicknesser operating at about 300-400mm off the ground. I have a DW733 and a no name table top planer (which for all it's failings does a lovely job). Workshop is small so I have always wanted these bits of kit on a single mobile base stored under a bench. I wanted to combine easy of storage with ease of use.
My idea for the swivel and locking device was to build a rigid torsion box base, run a steel bar through the center (made easy by the fact that I can drill the webs of the torsion box and then after it's finished pass the bar through it) and have this shaft run in a couple of bushes mounted on the frame of the mobile base. Locking would be by a couple of bolts passing from the frame of the base into the sides of the torsion box and screwing into a couple of imbedded nuts. I appreciate these machines are quite heavy and I might have issues rotating them so the base of my mobile base I was going to create a void and put a couple of council paving slabs in the bottom. Would also solve the problem of the two large council slabs that have been sitting outside my shop for two years!
The only concern I have is that it will make using one after the other a time consuming task, that being dependent on quickly and simply it can be unlocked swivelled and locked again. Greater minds than I will doubtless find another 10 reasons why my scheme is fatally flawed.
If I could do more than just spell Sketchup and actually use it, all would be much clearer but all I have is a scribbled drawing on a piece of paper and dreamy doodles in my mind.
I'll now sit back and await gallons of scorn to be poured on me from a great height or should I just call the asylum directly?