I think your idea is great. I found an eBay deal on a Phil Wood 145mm 40 hole dishless tandem rear hub, and a Hugi 36 hole tandem hi flange front hub. Everything got a little weird after that. I built my bike for 26" wheels, and discovered that that combination has one rim choice. Sun Rhyno Lite. Then I cold set my rear triangle for the extra 10mm. It was unbelievably difficult. I imagined that moving each 5mm at a time would be no sweat, but I was wrong. I laced them up with DT Alpine spokes, and ended up with a super wheelset.