Given the over shift and trim back that der shift levers have (or back in the day the technique we all did even we didn't know what it was called yet) I would not expect two ders to shift well at the same time if controlled by a single lever. Sure you could likely get some shifts to happen as intended but I suspect that synchronization would fall off soon enough. With modern cogs the shifting gate is purposely located, as each rear wheel takes different distances along the earth the two cog sets will become out of sync. While not the end of the world this would mean that one wheel would likely shift a part of a wheel rotation before the other wheel's gearing would shift. I think expecting the shifts to occur at about the same time to be wishful. Have you given any consideration to the differing strengths of one side of a body compared to the other side. By locking the driving, side to side, so that the two sides of the body rotate at the same rate or so that the weak side can be "supported" by the strong side means that there will be no steering forces due to one rear wheel having more power then the other wheel gets.


But to best answer the question I suspect an electric shifting system would limit the mechanical issues resulting in shift point timing discrepancies. Andy