Opinion of this setup?

That is about as good as it gets.  Be warned however, if you try to run a TMCC or Legacy engine on your "conventional loop" in conventional mode it will not respond as such.  It will always see the command signal.

 

Basically what you really have is 2 command loops.  You are just choosing to run one conventionally by varying the output to the track via the CAB2/transformer and control conventional engines.

this set up would provide exactly what you need. You can then run either loop as conv. or command and no matter, both are controllable via the legacy remote. the zw handles are set at full and the remote controlls how much of that is given to the loops.

The ZW-C will do what you want to do fine. In command mode when addressed the a and d handles start at zero and increase the voltage as the red knob is turned. The b and c handles are different. They start at the maximum or whatever you set the handles at and can be decreased with the knob. The middle handles work nicely for accessories OR Command Controlled Engines as you address the track and hit boost or spin the knob a little and the track comes up to full voltage. Conventional engines on the a and d handle also work great because the voltage starts at a little above zero and increase with the knob up to the handle setting.

Ron