Hi, I might have some useful experiences for you to consider. I have a 2007 Jeep GC diesel which I absolutely love. It pulls my 20' bass boat very well - my best guess is that the boat/trailer weighs about 3500-4000 lbs. I get about 18-19 MPG towing in the mountains of Arizona and have managed over 20 MPG on a couple occasions.
I purchased a 21' Ragen toyhauler about a year ago and have pulled it about a dozen times only for short trips of about 50 miles each way. The motor does fine; however, the suspension (with air bags) is not really up to the task. I have the WDH cranked up pretty high to meet the front/rear adjustment numbers. I don't get much (if any) sway, but there's a lot of creaking and popping going on back there and up under the vehicle. The trailer really pushes me around in the corners, and it's just a really uneasy feeling towing with this setup. Even with mirror extensions, it's hard to see - you've probably noticed the same with your current setup. I get about 10-12 MPG towing the TH.
My goal was to purchase another vehicle exclusively for towing within a year, and I'm really glad I will be able to purchase that soon. I know you mentioned you didn't like the idea of a pickup; however, I would strongly recommend that you reconsider. A diesel pickup would tow your desired trailer with ease and would really make your trips much more enjoyable as well as safe.
For what it's worth, I've settled on a GM Duramax as my desired tow vehicle. I had a 6.0 Ford and will never by another Ford. I was undecided between GM and Dodge;however, spending some time lurking on the Dodge Cummins forums scared me over GM.
Someone else suggested a garage remodel which might be worth investigating - I had a storage room on the backside of my garage, so it was less than $1000 to tear out a wall and gain another 6' of garage space.
I hope this helps - let me know if you have any questions...