It's possible. There are several different shaft-drive bike makers (
Dektra,
Dynamic, Incline (
Biria,
WebBicycle).) Some caveats apply when trying to motorize them, however.
A happy time frame mount should work as-is. SBC's shifter kit, though, probably won't, without some engineering work, using the standard, rag-joint sprocket. Possibly, creative engineering's
hub adapter could be used. All bets are off when it comes to the wider 4-stroke frame mounts, which typically need a wider crank.
As far as rack-mounts go,
Staton's chain-drive system could be used, with some adaption. (the sprocket mount would have to be the same as a frame-mount, per above, but, you would want to add a freewheel at the gearbox)
Staton's,
Dimension-Edge,
BMP, and others' friction drives could be used as-is.
The
GEBE system could be used as-is.