When AbstractWorkflowBranchProjectFactory.newInstance creates a new branch project, it should copy job properties from an existing branch project so they can apply to the first build even before any properties step has run. This would provide an alternative to JENKINS-41929 that would work even for Scripted Pipeline.
Ideally it would use JENKINS-33274 to determine the "base branch", where applicable. Failing that, it could use scm-api methods to determine the "default branch".
Would be useful for some cases of
JENKINS-33761, where the durability level is a function of the project as a whole. It would not work for cases where durability varies by branch, for example because master needs to run very durably while PR builds are run using a laxer but faster setting; in such a case, the initial PR build would run using the master setting.