Hi, @Andy Buckley - CAI Thanks for posting your question in the Microsoft Q&A forum.
I am sorry that you are not happy with the RU model, support for managing users in Cosmos DB for MongoDB Vcore is in the roadmap (Introduction/Overview - Azure Cosmos DB for MongoDB vCore | Microsoft Learn). However, if you are interested in a Private preview please do let us know so we can direct you.
Regards
Geetha