As always YMMV...almost all tracks I go to require a trip thru the PA mountains, and this certainly adds issues.
A note on enclosed trailer weights. A 20' enclosed Pace trailer is at least 3500# (from memory), without cabinets, walls, or anything else. Add a 2000# car, a decent tool box, say 200#, 8 wheels/tires a minimum of 25# each, and at least 100# of spare parts. Now add the jack, some fluids, fuel, some brackets and shelves to hold everything, and other such, and you're over 6000#. Want cabinets, a work bench, air tank, jack stands, awning, chairs, pit board, on and on? Bet you end up over 7000# without even trying. Figure at least 700# tongue weight.
No, a dually isn't a necessity (although it sure is nice!). But....I've tried 1/2 ton vans for towing, and wouldn't do it again. Even towing an open trailer, the suspension didn't hold up and the brakes just were not made for the task. After a very few years, three different vans were more than used up. Modern trucks are much better, but wouldn't consider towing an enclosed trailer with a 1/2 ton, at least not any substantial distances. I've seen many tow with 1/2 ton Suburbans, trucks, vans, and even seen people towing with cars. Rarely has something not designed for the task at hand lasted without major problems. There have been far too many horror stories about being stuck somewhere with a broken transmission or motor. So...
If you go with a 1/2 ton, limit the size of the enclosed trailer, and especially limit what's in it. Try to put the heavy items (spares, tool boxes, tires) in the truck. Seriously consider a cap for the truck. Strongly consider air shocks - I hate helper springs, they just seem to add huge amounts of oversteer. Buy really good truck tires, also buy trailer tires meant to carry the weight. Look closely at the large Toyota. A friend has one, uses it to tow a somewhat large enclosed trailer, and hasn't had too many issues with it except on windy days. I also recommend the Chevy. I've tried Dodge (late 80's), Ford (late 90's), and now Chevy (my other half has a 2003, I have a 2005), and it has the best ride of all. The Ford was the worst, especially the exceedingly weak 460CI motor.
Good luck with your decision!