Bon voyage, as they say!
Whatever would we do without SketchUp, amiright?
1. I'm assuming you've mocked up a frame using wooden 2x2's, not 2-inch square metal tubing. If so, have you considered the best joinery techniques? Personally, I'd recommend pocket screws. You have joints with 3, 4, even 5 members mating, and that's a bear to do with traditional wood joinery techniques - and I don't even want to imagine the clamping jigs.
2. Front-facing windows tend to leak the most, and unless you detach your tow vehicle from the camper, you don't get much of a view. Even moving the window to the angled portion on the front might fix both of those issues.
3. Speaking of which, I'd add in a spanning member on that angled portion. That's a huge gap. I don't know what you're using for roof sheathing, but you should factor in snow loads. If you park this thing outside, and it gets hail/snow/tree limbs on top, it doesn't look like you having enough cross members in there to support heavy loads, especially if you're going with 1/4-inch, even 3/8-inch sheathing. And since your roof is flat, with no curve anywhere, any deflection means that water is going to puddle on your roof and sit there, so you want as little deflection as possible.
4. Judging by the 7-foot width and framing design, I assume you'll be recessing your wheels? Plan ahead! If you want to use fenders, they come in standard sizes. 9x32 is the standard for round fenders for 13-15 inch wheels. But it's also not too much trouble to make your own wheel wells. When sizing your wheel wells, I'd make them large enough to accommodate 15-inch wheels. You don't need wheels that big, necessarily, but it's a nice option to have.
5. You probably already know this, but since you're over 80 inches wide, and you're six feet tall, you technically need additional exterior trailer lighting to comply with federal DOT regulations. You can run some of this wiring through your 2x2 frame.
6. Also, I'd look on eBay for surplus RV windows. You can find some big ones for some amazing deals. Shipping is expensive, but still, costs half as much as buying new windows. Those windows in your mock-up are, what, four feet wide? That's $$$$ if you purchase them new. Also, if you use RV windows - which I'd heavily advise, because house windows aren't tempered the same and are prone to breaking, leaking, and fogging up - you don't have to pre-frame the structure. RV windows use an interior clamp ring to secure the window. You don't need to screw around the perimeter.
6. The devil's in the details, as they say. You have a great start. Good luck!