[CA11] Redundant Autopilot install

I am installing a secondary autopilot and want to use the same drive unit. I have a Raymarine Smartpilot S2 installed right now.

The units will power will be wired in a way that will prevent them from being on, at the same time.

Do you see any concern about making the drive connection, via a busbar? So the drive output of each unit would go to a busbar and from the busbar to the drive unit. Would power being present at those terminals, while the Smartpilot is off, cause damage to that unit?

Thanks.