Jeff, I think you need to seriously downsize your expectations.

By the time you have such a trailer all equipped and loaded, it will be very, very heavy. Then you will need a very large and heavy truck to tow it with, and if that goes inside, the trailer will need to be even heavier, and the cycle continues.

My guess is the trailer will weigh at least 5000 pounds empty, plus your load of 3000 pounds, plus a truck that can tow it of 6000 pounds then the trailer needs to be beefier so it changes to 7000 empty and you have a total of 16,000 pounds to tow behind your bus. This certainly could be done but will be an overall pain to use.

My suggestion is you buy a van of some sort and tow it four wheels down. Then just put what you need in the van, and leave the rest behind.

Good luck. As they say in the airplane biz, "simplicate and add lightness"!!