that is a very good point.
Truck is 9400 with me in it and a full tank, skidder is under 12000, bringing the weight up to 21400, leaving about 4600 for the trailer, which isn't much I know, but its better then paying 4k for a crappy 6 month class and a little tiny letter on my license. I missed out on just taking the test and getting it over with, now you're required to take a course of some sort.
You're right, the CDL thing is a PITA. But WSP has no sense of humor and when they see a rig like you're putting together they'll pull you over and weigh you with portables just to make sure you're within tolerance. Even if your weight is okay they'll start looking your rig over for brake adjustment, lights, cracks, tires...whatever they can find. They'll check your tiedowns, tiedown methods, make sure your chains and binders meet spec and just generally look for anything they can find to write you for. They always find something. Always. If they red-tag you and place you out of service you're dead in the water until repairs are made. If you're working close to home you might be able to play hide-and-seek and get away with it but I wouldn't count on it. If they red tag you and you move the rig before you're cleared to the fines are enormous.
Back in the early 80s I was working for a company that heli-logged. We had a contract to log at Packwood and when we moved everything in...fuel tankers, service trucks, lowbeds...we got the full attention of WSP. Warshington was a lot stricter than California. For awhile, because they didn't know us, every time we moved we got stopped and inspected. Our stuff was in good shape and eventually they let up on us but for awhile the delays really screwed up our movement and cost us money.
I'm not trying to discourage you. I think your own trailer, for the way you're working now, makes sense. Just go into it with your eyes open.
Is having your own trailer going to make your insurance go up?