After reviewing your post again, I don't recommend the cart I go on about below. Anything heavy and stable enough to support multiple monitors, is not going to be easy to wheel out of the way. And any wall, ceiling, or pole mounted monitor arms will be massive and expensive. Anything with wheels all around is going to be less stable than fat man on a tiny skateboard. Any little imbalance will send the whole thing to the ground. I'd probably just use a few of those portable (and lightweight) extra laptop screens.

I made a rolling server cart out of an IKEA BEKVÄM. The shelves were spaced just enough to fit my printer on one shelf, the UPS and network gear on another, and the server (in an htpc style case) on top. It's heavy, with the heaviest part (the UPS) taking the bottom shelf. True, it only has 2 wheels, but it's built like a tank and rolls around easy enough without feeling like it's going to fall apart. The cart spends most of its time tucked in a corner, but the wheels make it easier to pull out to work on the various things connected to it. A monitor currently only sits on top, but given the weight of the UPS on the bottom shelf, I would not be afraid to mount some simple monitor arms that don't extend too much.

Side note: Trackball mice work a lot better where mouse pads fear to tread like couches, laps, chairs, even standing. I use a mouse all day for CAD work so these things have made it worth the adjustment from standard mouse: it being in the same place on my desk every time, being able to relax my arm and shoulder while moving the mouse across 3 monitors, and being able to use my laptop in the field from the seat of a vehicle. I have a Logitech Ergo with Bluetooth and a dongle (several actually), one at each desk or couch and one in my work bag.