This sounds very interesting; I don't know how much I could contribute, but I'd like to at least read along, and perhaps toss in a comment or question every once in a while.
In a way it goes along with a similar project I have been working on, that being a portable Emergency Repeater. In my case, I specifically want/need to avoid using duplexers; since the base equipment requirements includes spur-of-the-moment cross-banding (even to/from commercial band, police and fire band frequencies). In our area I/we already have an application/need for this sort of setup as part of our Emergency Response equipment. I have been looking into using vertical separation in place of duplexers; but I haven't tried it much yet. I've also been looking at passive repeaters, using two beam antennas and a piece of low-loss coax. Both of these have caught my interest, since I already have a portable tower platform to work from. In any case, I'm interested; but I am concerned that your project will become too big of a discussion for a single message thread. You may want to setup some message title infrastructure upfrount, so that sub-topics can work from similar related threads and still work with searches and filters. <<< vern >>>
