That's why I own one. I have spent many afternoons trying to use it, designing the system the way you talk about, having the math just so, the way you describe.
In PRINCIPLE it should work, the multiswitch, the diplexers, etc.

The problem is that it isn't quite so "cut and dry."
Just because my meter says I have the right signal quality doesn't mean the channel actually works for me. (Even though I have used your method, again, with the meter.)
Amazingly, however, when I run a dedicated lead and bypass your multiswitch and diplexers, some channels show more signal on the onboard meter, AND I receive channels I didn't receive before.