Okay, so you know how glass removes/makes transparent sides that are connected to other glass?
Is there a force an update on a custom glass node to mimic that behavior to work with a normal glass node?
So in a sense, when the custom glass is placed it will check for non-custom glass nodes around it and remove the texture from the side that is connected to it if there is one. As well as a check for when nodes are placed next to it.
Edit: Made the question a bit clearer.