Van Conversion/Small Motorhome as tow vehicle?

[TG2500]

I have a new 28' International (7,600#) towing happily with a pickup. Looking seriously at the benefit of a van conversion/small motorhome as a tow vehicle; something with onboard enclosed bath & basic food prep facilities to make the long trips more fun for passengers. I've read about Sportsmobile conversions (based on Ford E350) and was interested in any advice/input on Ford E350 (extended with V10 gas engine) as a tow vehicle (rated for 10,000# tow capacity with 4.1 axle) and/or any other conversion companies. I haven't found many options for a small MH/conversion with a large towing capacity - most tap out at 5,000#. I thought an Airstream Avenue might be interesting but nervous that 7,700# tow capacity is cutting it to close to tow the 28'.