come a long way from your original question haven't you? that i why the forums are so good. other people have ideas you can consider before making a decision. but 30 inch??? overkill, maybe.
if this is what you really, really want, please ask your handy husband to make the table bigger than what is shown on the clay king website. at least at one end so you will have working room after the slab is produced. find out how to remove the huge wheel handle so you can get at the slab to work without hitting your elbows. it is very handy to have flat work space right there so you don't have to lift the slab to another working surface. my northstar is fitted with a set screw and i just slide the wheel onto the shaft without tightening the screw when i want to roll a slab. (my Bailey is the same.) otherwise the wheel is stored standing on the floor at the end of the table since the tabletop is in almost constant use.
don't bother with a box to cover the working part, a clean heavy cloth will save your lifting muscles and the working parts.
the picture shows the smallest table i have ever seen and the most industrial looking heavy duty rolling gizmo. who makes it? why haven't i heard of it????
it is easy to drill the metal legs to support shelves. i put one about 15 inches from the floor. to hold plaster forms. then i put a smaller piece of plywood with wheels and a rope handle on the floor to hold boxes of clay. it rolls out when needed but is out of the way. every inch counts in a small studio.
the manufacturer's name is not shown. who is it?
good luck and make lots of things.
The Clay King Slabmaster is made by Friendly Corporation, same as Shimpo rollers and Axners rolling Thunder. The studio I belong to has the Shimpo version which looks a lot like the Slabmaster and I have used it and like it. I'll take into consideration a longer working surface. He suggested the cover so I wouldn't have to worry about hitting the rollers and maybe that I could use the cover as a shelf to hold whatever tools I needed while using the table. The shelves are a must and kind of planned to measure whatever space I had on the table Slabroller I get and install what ever configuration would work. I LIKE your idea of clay on a rolling platform makes much more sense than hefty those blocks around.
My main work surface is a worktable I got a SAMs it's tall enough I can stand to work or use the tall rolling stool I have. I think its 5 feet long and super heavy duty with steel legs and a butcher block top and can take a beating so seems to be working out. Unfortunately the top is sealed under varnish so clay seems to like to stick to it and I have thought about getting out the sander and attacking it but for now a piece of canvas seems to be working. I want to get a piece of that board from a Home Depot next time I head that way but haven't made the hour plus trip out that way recently. I even added a shelf under it, with the bonus of its at a good height for me to put a foot if I want. I keep all my plywood and drywall ware boards standing on the shelf and for now clay, my rolling pin and slats on the other side. If I make the rolling platform like you have for my clay I might add a couple more shelves on one side and keep additional supplies there. I even made a small shelf for the end out of 1x4s with each shelf being tall enough to hold pints of underglaze and glaze it ain't pretty but the shelves are level and I used zip ties to attach it to the table legs so it doesn't fall over. Kind of maximizing my one work surface. I would REALLY like to find another table to have dedicated for glazing but not sure where I would put it, might have to get rid of my easel lol. You have no idea how shocking that idea is to me as a painter; my friends would be convinced i was an alien if they even heard that I would consider sticking my easel in the closet.
I also need to figure out someplace to put some shelves to dry ware on, currently I am using a repurposed drying cabinet from my darkroom days to store pieces under construction as well as slowly dry finished pieces. I bought some of that plastic grid made for light covers and use that as the shelf so the pieces don't fall through the widely spaced wire shelves that came with the cabinet. But I can see quickly outgrowing the cabinet as I get stuff made. Just have to decide if I should get one of those rolling wire shelf units from SAMs so I could move it around as needed or just cut up some of the scrap plywood in the garage and screw them to the walls. Will have to think that through some more.
So yes I know and understand multi purpose work spaces and the suggestions you made will be remembered and taken into account as I try and get set up so I can work without moving stuff around every time I want to work on a different piece.