A guy in California named Leo Fender kinda sorta addressed this issue back in the 50's sometime, I believe? Something about a more portable instrument that was louder than the UB and could be played with "precision" even at Jazz gigs?
I don't think his idea was for it to sound like the UB and, in fact, he didn't want it to.
To me, I think the proper solution to sounding like an UB is to just get an UB. But, hey, call me crazy.... NS designs and others have electric versions of UB's out there too, that may also fill the bill. Sound great, a lot like the UB, easier to carry and a heck of a lot cheaper too...
L