Phoenix Cruiser Class C has an emergency sewer dump:
You already have a lot of what you'd need on your Roadtrek Ron. (I have to use your photos
You can see in the photos that your RT emergency clean-out is after both the gray and black tank valves. That's good.
You need to figure out how to extend it to a point where you could reach in and and attach a dump hose.
You'd have to operate the black and gray valves from the driver side but connect a standard hose to the passenger side.
The clean-out looks smaller than 3 inch so you'd need a fitting to get it up to 3 inch. Also I think it would be best to add a third valve before the RV sewer hose connector.
You'd probably only use the emergency dump if the macerator failed. If it failed then the pipes would have some waste in them so a third valve would let you attach a hose without first dumping any waste on the ground.