The AMS lite does have a motor for each color. It currently only runs forward to feed the filament, but there is no reason it couldn’t run backwards and pull the filament back a little more.
If they had some sort of hub that attached to the top of the frame with a Y splitter for each of the 4 inlets they wouldn’t need to back up very far to swap to a color in the second AMS, so it wouldn’t need to worry about rewinding the spool itself, it would just need to back up an extra couple inches to let the other color feed in.