Thanks Invisiblehand! That's not only extremely cool, but I happen to have good skateboard wheels lying around. Now, all I have to do is figure out how to get my Birdy to walk up and down NYC stairways.
Thinking again about the mini, the bag idea might work similarly to the Tikit with respect to rolling if it were tailor made. Because the handlebar fits between the fold, a tightly fit bag would probably hold it together well. But that's only an untested hypothesis...