Limiting the use of shared runners

Is there a way to limit usage of shared runners (on, in particular), beyond just enabling/disabling them for a project?

With the recent changes in CI/CD minutes accounting and quotas, it becomes more important to properly manage resources. Suppose I have a pipeline with 20 jobs, each of them takes 1 hour to finish, and suppose I have a single specific runner.

  • If I disable shared runners, the pipeline will take 20 hours to finish, and I’ll be charged 0 hours of shared runner use (the specific runner runs every job).
  • If I enable share runners, 1 hour to finish, charged 19 hours (the specific runner runs one job).

If I could fine-tune the shared runner use, I could, for instance:

  • Limit shared runners to 1 simultaneous job: 10 hours to finish, charged 10 hours (jobs run in pairs, one for the specific runner, one for a shared runner).
  • Limit shared runners to 2 simultaneous jobs: ~7 hours to finish, charged ~14 hours (jobs run in trios, one specific, two shared).
  • Add a second specific runner, and limit shared runners to 1 simultaneous job: ~7 hours to finish, charged ~7 hours (trios, two specific, one shared).

I don’t think there’s a way to do this or something similar, is there? Is there some issue/feature request that could do it? Would it be of any use to create one?