Smaller Class A would probably be a gasser which means that your dinghy would have to be less than 5,000 lbs. In terms of towing 4 down, the newer vehicles offer less choice than the older ones. Right now, it appears that GM offers the only cars with automatic transmissions that can be towed without any other add on items (drive shaft disconnects, transmission lube pumps, etc.).
I have had many different towed vehicles through the years and I always liked the Saturn for easy hookup and go even with an automatic transmission My favorite is also my current dinghy, the Hummer H3. The only vehicle that doesn't have a steering wheel lock, 4 wheel drive, and nothing extra needed to tow one with an automatic transmission. The only downfall on the Hummer is the weight which borders close to 4,900 pounds, which I did tow behind a gasser and I really felt it behind me. Of course, he Saturns and Hummers are not manufactured anymore.
Motorhome Magazine does a listing every year of all the vehicles and whether they can be towed 4 down. They may have previous years listings on their web site.