Even if you value your time at $0 / hr I think you'd be further ahead financially getting a small TT or even a TC mounted on a trailer with storage bins where the cab and wheel wells would be.
Do you not have a cube van because you need it to carry your wares to these places for sale? What happens to your storage when you do the conversion?
I 'camped' in a semi converted cube van for years before I realized I was further ahead with a short Class C pulling a trailer for the tools and parts I needed with me. Camping stuff eats up space fast.
Ted 'n' Laurie, plus Jackson (aka Deputy Dog, the Parson Russell Terrier 'fur kid') and, Rylie (who crossed the Rainbow Bridge June 14, 2012).