I understood, will be sufficient a plug-in that change the audio from main to pip picture.In other words, what Littlesat says is that it cannot be integrated in the standard OpenPLi image because there is no "universal" solution possible that will work on every supported box.
So somebody interested in your request and having the same hardware, needs to write this feature as a plugin which will be box specific (like I had on my ET-9000).
Unfortunately I tried to “play” with the pipsetup.pyo but without results, only with strange position of the pip![emoji23]