Backfill bgworker Extension?

To be clear, what I mean is batch updating a large set of data in small pieces so as to avoid things like lock contention and replication lags.  Sometimes these have a driving table that has the source data to update in a destination table based on a key column, but sometimes it is something like setting just a single specific value for a huge table.

I would love instead to have a Postgres extension that uses postgres background workers to accomplish this, especially if it were part of core.  Before I venture into exploring writing something like this as an extension, would this ever be considered something appropriate as an extension in Postgres core?  Would that be appropriate?

Thanks,

Jeremy