[Gordon]

       
Richard,
Currently I have no side to side tag axle control with the exhaust, so I would not be loosing anything. If in fact I used 2 exhaust valves & wired them to the drive EXHAUST solonoids it would work.
would need to put diodes on the wires going to the tag switch, I think.
I will have TWO raise valves on the tag so I will retain the side to side control.

I added ? 2 pictures, one is my proposed plumbing for the tag & the second is switch positions & their various functions.