This is my current setup:


I've been pulling that with a Ford Fiesta with zero issues over the years. My lease on the Fiesta is up this December, and I'm trying to decide whether to get an E150 and an enclosed trailer, or stick with the system I have of a very light duty tow vehicle and a small trailer.
My goal with any trailer would be to have an enclosed area for my bike while hauling, and then an enclosed area to sleep in. No plumbing or anything fancy. I have a Honda generator that I use to power tire warmers during the day, so I can route in a plug to get electricity for charging and other basic stuff, but that's it.
So this is a concept I've come up with. WARNING: ABSOLUTELY TERRIBLE DRAWINGS AHEAD. I was just trying to get them onto paper before taking the extra step and putting them into CAD.

The basic concept is a 4x8 (or maybe 5x8 or expanded to 5x8) open cargo trailer. Around that I build a raised sidewall (height undetermined, but at least two feet). Then plopped on top of that sidewall is a half-cyllinder (this is NOT a hemisphere) that is divided into three sections to allow it to slide open.

I'm a mechanical engineer so I can bug people into letting me use CNCs and whatnot for a lot of the components. I was thinking for the actual curved pieces some sort of slightly flexible plastic would be best, and I could even install a clear piece of plastic on top as a window/skylight. Also, the rear panel would obviously have to detach to load the motorcycle on, so the panel would have fittings to allow it to act as a ramp.

For sleeping, I'd basically have two halves of a bed with cushions attached on top that I could mount basically flush to the outer walls, so the inner walls of the trailer would be the solid part of the bed, protecting the cushion in-between the base of the bed and the outer wall. I'd either design a mechanism to let them swing up and rotate into a bed that locked together, or just make it so I could stick some mounds on the bottom to bring them level.
The "shell" would be able to lock fully open or fully closed, so if the trailer was hauling something taller then the shell it could still be used, as long as the first third portion of the shell didn't interfere with it.
My main concerns with this build are:
1. Having good rubber seals between the shell pieces - The middle portion would be the outer-most part, so that any water would have to go up inside the lips, so I'd have to find a good rubber seal that could both prevent moisture from getting in yet be flexible enough to withstand being slid back and forth. If rain is absolutely poring, I always have a 10x10 E-Z Up at these event that I could cover the trailer in though.
2. Ventilation: This is the trickiest part due to how the shell pieces fold together. I could build some sort of low profile fan into the rear shell piece (as it winds up being the inner-most piece) that sticks into the trailer a bit, but that's the only option due to the other parts either moving or being incased by other pieces.
3. Cost - Would this actually be cheaper than just getting an enclosed trailer? - Probably not. It actually mostly depends on if I decide to splurge and get a dedicated tow vehicle in the form of a cheap used E150 or E350. But there's something to be said for just having one vehicle with a 2000 lb towing capacity and decent mileage.
My goal is just to make this as flexible and well thought out as possible. My open trailer has evolved into a more and more useful setup over the last year (the photo I posted is just the most recent one I can find, I've since added more E-Track, a different ramp with a better mount, and I plan on adding a tongue box before this season begins), so I'm just giving this thing plenty of time to digest in my brain before considering putting something together this winter.