From an engineering standpoint, it's virtually impossible to create a freewheel with such a small diameter difference when compared with the hub threads.

Per Sheldon:
"There is a special BMX variant of flip-flop hub which is intended to take a single-speed freewheel on each side. This type has a standard thread on one side, and a smaller thread on the other side, which fits special undersized 15- and 14-tooth freewheels. (There is not room to fit a freewheel mechanism inside of a 15-tooth or smaller sprocket, with a normal sized hub.)"