I would also put a notion toward using strut. Unless you or someone you know works in a metal fab shop, the easiest solution is to use strut with a base plate. There are so many options there for mounting stuff. Electricians use it all the time for that reason and it's available from the big box stores so you can actually see what they have and what's available to use.
Sounds like it would really limit your ability to re-arrange your shop. I have moved things around since first setting up the shop, much better the 2nd or 3rd time. I have no reason to move my equipment more, really works nice now. My plugs hang from the ceiling, so I could move the table saw, and although I do not enjoy attic time, has worked out well.
I should have been more clear in my previous post. You can put 120V and 240V circuits in the same box or conduit. Different story with 480V though. I'm going by the CEC (but it and the NEC are mostly harmonized), but you can't put circuits that are fed from different transformers in the same conduit. 120V & 480V are mutually exclusive and are derived from different system.
You can mix voltages in the same conduit as long as all wire is rated for the higher voltage. The unistrut is a good idea. My concern would be how do you plan to transition from 2"pvc to a 2 gang box
I'd use 1-5/8" strut. Mount a strut floor plate like this P2072ASQ-EG. You can use 1/4 or 3/8 spring nuts if necessary to mount your box. You could chop off half that plate to get closer to your 2" conduit, or use 2 plates and mount stuff between 2 uprights. Mount to floor using wedge anchors or even probably tapcons. And if you still think theres too much wobble based on how high you go they sell 45* brackets to run a support to the floor. Personally I've installed uprights with wedge anchors and at 4 foot high there's such a small amount of wiggle it will work fine
When I mounted the disconnects for mine I mounted a steel plate to the saw. The disconnects are on one side and an outlet on the other. Because this was in a garage I was required to mount it a minimum of 18" off of the floor, just in case I had any gasoline stored their.