Good thought and one I can consider. I haven't thought of actual implementation of a single side drive much... The tandem crankset wouldn't be my first choice to get that job done, however. This comment is because the 24mm spindle on the tandem crankset is much much longer and the Q factor of it is much wider than what I or my stoker would like.
I have a lot of cranks and crank arms right now, I could easily explore this option and chainring/spacer combos. I have no desire to run anything but a 39/53t chainring.
Right now I'm seriously debating the easton r90 rim vs some light-bicycle 55mm carbon clincher rims. It's the rim construction that most scared of. I don't want to get a "China carbon" part to be aero and cool to have it fail and hurt us.