I have been planning one in 1/24 myself. I am a big fan of the Showhauler, Renegade, NRC, etc class 8 truck conversions or toterhomes. Anyone looking for more info should visit truckconversion.net
Anyway, in 1/24 or 1/25 scratchbuilding seems to be the only way to go. The cab and chassis components are available commercially through kits and in the resin aftermarket, but the coach body is another story. My plan is to use Melbourne Model Truck Accessories custom studio sleepers for the base of the coach, scratchbuilding windows, bays, slides, etc. and use a galaxie 21ft tag-along trailer, but a big stacker trailer could be built in much the same manner as the coach.
I would think there would be at least a resin market for these, but remember no one makes a modern RV or bus of a US prototype either. I think the physical size in 1/24 holds people back, but what an impressive model in that scale, though! I found some postings of a guy who built an awesome toter and stacker on a Mack chassis in 1/32 somewhere online. Also Truckin Little makes a resin coach body and stacker in 1/64 scale for DCP trucks, but I know that doen't help either.
My model is still in the planning stages, making parts/supplies lists and researching, lots of reseaching of the real thing.