If I'm understanding correctly moonlighter's proxy speaks Ubiquiti's protocol on both ends, "just" altering the video stream along the way. Which is pretty cool but not what you're looking for.
I'd like to make a production-quality version of what you're looking for: acts as an RTSP server, adopts Ubiquiti cameras. As a single-binary thing that you could run anywhere, maybe even on the camera itself. (self-adoption? emancipation, as in "emancipated minor"?) But it'll take me a bit. My RTSP library right now is client-only, so it needs a bit of expansion to do this. Server support is in my TODO list along with several other changes. https://github.com/scottlamb/retina/issues/89
