I have been using Archicad for over 10 years & while it is great for architectural modeling it is not a render package, as much as they try and talk up the cinerender system within Archicad it is slow and is being replaced with live render systems. So packages like Enscape are a perfect companion. At present we feed our models through sketchup but this does limit the texture channels available. I assume rhino can take the extra channels but I'm not in the market for a $500 rendering software when I use the Enscape output anyway.
When you do supply an add-on for Archicad can you please ensure that your system pulls through the extra channels (displacement/normal etc) that we can setup in the cinerender area of the surface settings (see attached image). I am assuming these textures/settings are accessible for you to pull though to Enscape? If not I suppose you would need to build your own material settings options as a part of an add-on.
I am a big believer that Enscape sticks to being a straight live renderer and I do all the setup work in archicad with both objects & textures. When it comes to proxies there is definitely some merit in that but base it on an 'Enscape archicad library' that you can sell seperately. Plants/lights & maybe people but I find unless they are epic models they can easily ruin an image/environment.
Happy to be a beta tester for any add-on developments on the Archicad side. I really can't wait to have a live VR feed from Archicad. It's going to be awesome!