[Christ]

To attach the rear pieces, you can just attach them to the door and break the angle out a little more. It won't be as much of a help, but the area that gets lost in there is minimal.

That will make it so you don't have to get plexi or worry about blocking the lights, but you should put reflective tape on the trailing edges of your additions to draw attention to their depth. The upper one can be attached like an awning to the top of the trailer, and won't interfere with the door opening downward. The parts on either side that attach to the doors can be hinged to fold into the face of the door when it needs to be opened, and can have bolt locks on them to lock into the upper part when the door is closed and they're open.

A single screw-on plate across both tires on both sides of sheet metal or even coroplast will work fine for the wheel covers, and is easily removable in case of tire service.

The trailer sits kind of high, I think. If it doesn't have suspension, you can disregard this, but if it has springs, you could lower it's height and put air-helpers in there for when you need more clearance. The lower the trailer is, the less topper you need, and less frontal area you have to deal with.

If it doesn't have suspension, you can just add some semi-flexible skirts (conveyor belt material works great) to the length of the sides to keep excess air from getting under there.