It would be nice to have other people being able to use it, but it is not a top priority for me. Also battery drain is not that much of an issue as it will only be used while at home. The last point is a bit more concerning though, so I will see if I can test this out and see how well it works. And yes, the connection seems to be the biggest issue here. But it seems that once configured, it only requires running 'scrcpy' on the recieving end. And KDE Connect can be setup to run commands remotely, for example I just set it up to open VS Codium in a specific folder from my phone. I can't seem to add that command as a quick access tile (which would be my preferred option), but I could add it as a widget on my home screen for quick access so that conncetion is a button press away. How long the connection can stay for I don't know, but I will see if I can't test that out this week.
Did you check out balenaSound by the way? If so, what difficulties did you run into that made you discard it?
fcast looks nice, but if I understand it correctly it would require implementation in every specific application. I think if I were to jump onto the Grayjay-wagon, that could be nice, but I would love for my solution to be app agnostic.