Join Date: Dec 2007
Location: Minneapolis, MN
Bikes: Trek T2000, Ventana ElConquistador, ElSanto, STP400, 5500, JubileeSport, Scattante...
Another option would be to build your current hubs with some narrower rims, like a Sun 0 Degree XC or Velocity Aeroheat. That would be a good compromise for swapping between 28mm road tires and 2" fat tires, like Tandemgeek suggested.
I think you'll find 26" tandem road wheelsets rare on the used market.
We just picked up a bike with 26" wheels to try as a convertible. Traveling will be easier with just one tandem that we can use for road and off-road, with just a wheel swap or tire swap.