I second the FG trailer idea. We've got a 35 year old Scamp knockoff that is STILL going strong, in the 5 years I've had it, it's been drug over, around, and through more stuff then many campers see in a lifetime, with no ill effects. I daresay it's more durable then an Airstream (wildly dodging the Silver Bullets thrown at me by the AS crowd

)
Depending on just how much room you need, perhaps a 15' Scamp would be the best. If you mounted it on a chassis similar or just a touch longer then Hunter's, you could mount a 3' dromedary box on front for bike storage, it could double as the basement area for your non-biking trips.
Matt