As the Greenberg Repair manual says of the AC motor version, "the tables must be connected rigidly together" and nevertheless goes on to discuss your adjustable 3-ohm, 10 watt resistor "if the motors do not synchronize closely enough."
For a snap into place mechanism I was thinking of a electro-mechanism that would push a pin into a hole in each stub wall to perform the final alignment and locking. So there would be a lock trigger and unlock trigger whether manual or automatic but only when the motors are stopped. Obviously this is over-thinking the problem but keeps the mind active. Like moving cars back-and-forth to position them over the uncoupling electromagnet, it adds to the "play value"...
