I guess we can start a thread here about ideas for the next era of Flathub.
When we move to Forgejo (doing it before is probably a waste), it would be nice to be able to test each PR, merge it, but not build to be published to stable immediately.
I can see where giving app maintainers the ability to randomly start stable builds might not be ideal so it could be that before starting the build it checks to see there are changes in the branch requested compared to last stable build date.