Sorry, missed part of the sentence.
There are several ways how one can implement it. I would personally prefer pull requests to dist-git over scratch builds. I think it is important to keep some visibility in the system, so that not just the owner of a change, but also random lurkers can see what is being prepared.
(Also solves the issue )
Please read as: Also solves the issue when there are overlapping sidetags prepared by different people.
One can subscribe to pull-requests in a project, and get early alerts about planned changes.