A couple of concerns
1) Trailex -Run this thru the USACA first. I have heard of stability problems with A-Class and aluminum trailers. I have not heard any "first hand accounts" where a steel trailer would not have had problems too or they were doing something so strange a semi might have had problems. I have heard a lot of vague "so and so had problems" stories.
2) A locally built welded galvanized or welded aluminum trailer will almost certainly be much cheaper. Make up a drawing or find a photo of what you want. Call the local builder(s) and fax them the photo or drawing. As long as they can figure out how to do it by welding things on or cutting tubing, the price is normally reasonable. One of the local builders near Houston built a nice double stack A-Class trailer.
3) I use a Tornado trailer (1500 lbs). There is a piece of mind to knowing the shrouds will break before the wind blows an A tied to it over. If I sell it, I will consider a trailex. It's so wide my A sits inside the fenders and you always know it's back there when you are towing it.
4) Quality counts. If you want something beyond Trailex, Texas-Tilt builds a A-Class trailer. It will cost