[Craftsman88]

as i know nothing about electronics all i can do is guess
if a cu puts 12 volts to the rails ,i would assume that if you connected another cu to the same rails you would be trying to put 24 volts to the rails
as the cu would not cope with such voltage it more than likely go into overload and shut down
in the mean time one ,maybe both cu units could die
as i previously stated ...costing you a lot of money ,or in other terms ,about 6 slot cars

It wouldn’t be 24 volts, it would be 12 volts in parallel. But as previously stated the digital packets would get blocked and confused. If you can develop a WiFi type system to communicate from hand controller then it might be possible. Good luck.