^ I liked the "Long John" - "steers like a boat." + 1 to that manufacturer for honesty.

OP, this might sound crazy, but couldn't you just make a custom built trailer that would allow your bike to be more maneuverable and save weight? If you have the mechanical skills to build that tandem frankenstein I'm guessing you could build one heck of an aluminum trailer.

I'm presupposing here you only want the longer wheelbase on the bike for cargo carrying capacity, though. Maybe you just want a bike that handles like a pig on roller skates.