Which is irrelevant because GOS does not by default implement Google playstore and play services that have that limitation.

If Google implements the same play services sideloading limitation in AOSP which is unlikely, it can be removed like anything else because it's open source.

You missed the primary issue OP mentioned, which is that ASOP is becoming a smaller and smaller part of the entire OS, and there's an ever-increasing amount of work needed to make it work on a real phone.