No matter how well intentioned I firmly feel that those arguing that a dual axle 7000# GVWR is required for a 2200 pound load due to improved safety due to experience with tire blowouts should be a little more diligent inspecting their tires paying much closer attention to tire pressure prior to hitting the road. The primary cause of tire failure is under-pressure. And for those who check tire pressure every year or two and replace tires every ten years I'd recommend a quad axle to provide the necessary level of safety, it's all relative.
I am going to agree with you to a point on this, everything you said is valid when it comes to the maintenance that most/some people do.
But while a trailer with 3500 lb axle would be sufficient to carry the tractor, what I had found when looking at the single axle trailers is that they wouldn't carry the load unless you bought a really good trailer that was properly made.
Randomly looking at the specs on a 5x10 trailer, the trailer weighed 800 lbs and with a GVWR: 2,990 LB, you are at 2190 lbs worth of cargo. While sure you could over load it a bit, you wouldn't want to do it regularly. Obviously this trailer is a little small but it goes to drive my point, a bigger trailer, more weight, one axle, less loaded recommended weight.
Most of those $900 to $1200 trailers aren't even rated for much more than 2000 lbs of loaded extra weight. Give or take some on the weight, but why buy a trailer that is barely capable of carrying the load? If you are going to get a single axle, definitely make sure the trailer can carry the load.
My biggest concern as stated above in a previous post and in this post is that the weight on a very small trailer for a tractor usually means that all the weight is on the tongue or on the opposite end. You can't tell me that a tow vehicle squatting in the rear or being lifted by a trailer is in anyway safe to use. Having a trailer loaded to the max doesn't make for safe trailering either.
While the dual axles would help in case of tire failure, that shouldn't be the reason to buy one. You should buy what will let meet your needs and let you do it safely (for you and others on the road) and allow for a little more balancing of your load so that you are actually pulling your load instead of carrying it with your bumper.