I appreciate all the feedback guys. Your opinions on trailers matter in helping the decision process which is not always that easy.
Duffster,
To answer your question. It makes sense to do it that way from a commercial vehicle standpoint if you are considered a commercial vehicle. I can not speak for other states, as I do not know their laws like I know MN commercial vehicle laws, and I am still learning things about the commercial laws here in MN.
If you are a commercial vehicle (You are for hire, making a profit: can be anything that is considered furthering a business (someone buying you lunch, or paying for your fuel (you are technically being reimbursed for your services)) you are governed by weight on either a single vehicle (power unit) or a combination (power unit + trailer). When weigh 10,000 lbs. on just the power unit, you need a health card (also known as a medical card) saying you are fit to drive a commercial vehicle. That lets you operate a power unit 10,000 lbs or more (again, if you are a CMV).
Now there are different classes of license here: A, B, C, D. "D" is operating anything up to 26,000 lbs, "C" is more of you hazardous type of license if I remember right, "B" is for any single vehicle weighing 26,001 lbs. or more, and "A" is for your big rigs. and you are able to drive any vehicle that is registered for and permitted for whatever weight.
Where this trailer thing comes into play is important with the class of license. I myself have a class "B" license. I don't have it b/c of my personnel vehicle. I drive a charter bus from time to time. The class "B" license allows me to drive any single power unit, weighing whatever it comes in at. The bus I drive weighs around 33,000 lbs without passengers. If I put a trailer on the power unit (or bus), I am only allowed to tow up to 10,000 lbs. If I go over by one pound (as an example), I technically have to possess a class "A" license, because I have exceeded the weight allowance of the class "B" license.
That is why any truck-tractor driver has to possess a class "A" license. The power unit comes in at whatever weight it does, but I would say all of those semi trailers come in over 10,001 lbs., therefore requiring the higher class license.
If the trailer manufacturer keeps the potential load carrying weight (GVWR) at or under 10,000 lbs., he keeps from having to have the consumer go apply for a higher class license, which only allow for more commercial regulations. It's just like todays pickups. The 1/2 and 3/4 ton pickups GVWR is under 10,000 lbs. If they were rated over 10K, and you were considered a commercial vehicle, you would need a health card. That why one with a pickup, needs to be careful in their choosing of a pickup. If you go a 1 ton route, those trucks today are rated for over 10K by themselves, and if you get involved in being considered a CMV, you need a health card at minimum.
I don't want to confuse anyone anymore by this, so I'll stop there w/ the weight ratings and all.
This was a longer explanation that I was planning on, but commercial vehicle laws are so in-depth, that I felt it only fair to be detailed in my explanation.
I only touched on a little bit of our laws here in MN. Certainly, if you are thinking about or are in the CMV status, check with your state agency (usually state patrol), or local agency to make sure you are legal and legit. They will set you straight and it will keep everyone happy on both sides.