Nick, I totally agree with all your apprehensions about AOR and the 5700D in particular.
I gave up on AOR because of the DV10, and their arrogance and aggresion re. the problems it had, and Customer concerns.
However the AR-DV1 is a proven, excellent and versatile radio. I use the R8600 and DV1 all the time. In my case a BNC cable from the DV1, with an antenna switch. One side going to its own antenna, and one to the 10.7 MHz output on the R8600 via BNC cables. It does not have to be done that way, one BNC cable can be used of course, just easier then manually swapping wires.
If the two radios are connected, and the DV1's frequency set to 10.7 MHz, any frequency you have shown on the R8600 goes to the DV1, and all of the DV1's modes, Digital and Analogue are then available to the R8600, plus other functions.
One nice little 'extra' is the small 'bandspread' ability this gives, as you can also tune the DV1 a little either side of 10.7 which can on occasions be a useful 'clarifier', using the many 'steps' available on the DV1.
One turn of the antenna switch and I have two excellent independent receivers.
Not a cheap option I realise, but if invested in, one that can give superb results.