Bob,
Wow that sounds really fantastic to get a plug-in which interfaces with ML and the ISY. That would be the best solution.
I have two Russound CAVs so you basically have the same hardware.
I'm happy to beta-test your plugin once it's ready for testing and yes I will understand and expect that it won't work a 100% correctly until the bugs are sorted out.
Anyway I don't know how your plugin will work, but here is how I had a few things working with the InsteonPLM plugin from ML. They are currently not working as I stole the PLM from ML as I simply got sick of working with the quirky interface and managing links is no fun with it. (Try to setup a scene with 20 something devices with ramp rates and different on levels for a go to sleep scene. A nightmare!
1) In the Office, I have a Russound Control Panel and two lamplinc modules. Many times I'm in the office and it gets dark and I don't automatically have those lamplincs come on or I'm just too lazy to get up and turn the knob so they turn on. So instead I turn the iPhone on and go my ML homepage, go to lighting and tap the Office On button. A little macro in MLServer executes which sends a GroupOn command (that turns my lamplincs on) and also turns the russound zone for the office on. Here is how the command line looks:
Macro|Lighting.group.2|GroupOn!MLCAV66|ZonePower~2~6~On
This Lighting Group also turns on a light in the main house (as the office is in a small detached building from the main house) on a keypad. It was button G. Sometimes you just don't want to run over there and turn the lights off and/or the Russound Control Panel.
So when you hit that keypad button in the main house I put the following in the InsteonPLM in the Devices Tab and then click on Controls. A new window should open. Under Command Button 7 Off I have/had:
MLCAV66|ZonePower~2~6~Off
I didn't put the Lighting in, because I was playing with the whole setup. But it worked great.
There is a new thing I thought I could do now. Isn't there always? My wife likes to do meditation for 30 minutes. So she goes in the bedroom turns the Russound on changes to the iPod source (it's plugged in to the Russound iPod dock) and has a timer to remind her when the 30 minutes are up, because the iPod dock keeps on repeating the playlist forever. It never stops. Instead I could program one button on a insteon keypad in the bedroom which turns the Russound zone on, sets it to the correct source / volume and starts a MLTimer for 30 minutes which would then turn off everything again.
And of course there would be things like if you hit go to sleep button on a keypad that ML makes sure that all Russound zones are off etc.
I don't know how the plugin will work, but I know that with the ISY you can create programs if a certain button on a keypad is switched on/off that it does whatever you'd like to do it. So maybe if your plugin exports the lights/scenes to ML as variables then we could monitor the state of a button on a keypad with a variable and if it changes to on or changes its value a MLServer Rule could kick in and for example could execute the turn on x zone on the Russound command.
Let me know,
Michael