The ws seems to have release and events endpoints for collections, but some things (such as works) don't exist yet. For example:
https://beta.musicbrainz.org/ws/2/collection/6d7ee31a-a251-4c38-b751-e0551f64c77d/works
is a valid work collection.

We have a collection of ~2000 works that we'd like to create.

I suspect this will be the case for other collections as well. Perhaps we need to make sure that adding a WS endpoint is a part of the release process for each of the new types that get added.