You could easily pull a YJ with a car dolly type trailer, you just need to have enough tongue weight to keep it stable.
The reason people cant pull with certain rigs and try to correct it with swaybars and such is they either dont know how to load properly, or the unit they pull is unable to be loaded properly.
Ever seen someone go snaky when hauling a trailer? Thats a result of insufficient tongue weight. What happens if the trailer wants to sway, and without a enough weight on the rear of the vehicle, it causes the swaying to become uncotrolled.
Tractor trailors have a wheelbase close to that of a pickup truck. Yet they pull loads of 150,000 plus pounds.
In relation to light duty thats like sticking a 35 foot gooseneck behind a jeep TJ.
The reason the big trucks can do this is by distributing enough weight to the truck axles, and the use of trailer brakes.
If the jeep has a base rating of 5000lbs, that means you should be able to 1000lbs plus or minus on the tongue. Using a minimum of 10% for tongue weight as a rule of thumb will provide good stability. More is better, but you will run into axle rating issues if you try to put more then that on the tongue.
A modded YJ should be under 4000lbs and a car dolly is is under 1000 lbs. All within the 5000lb rule. Distribute the weight to the tongue properly (minmum 10%), use trailer brakes, and you should have a safe reliable unit for pulling a jeep with a jeep.
hth
I drove truck for 10 years in the oil pacth and logging industry. You can apply this principle to anything you haul. Be it a big truck with 150000lbs of logs, or a minivan trying to latch onto a tent trailer. The fundementals never change, only the applications.