It would be great if we could organize the projects and not have them all at the same level of organization.
We could use this hierarchy to put rights, consult costs ...
A bit like the idea of Azure's management group or GCP's "Folder".
You may want to take advantage of new functionality that we just launched for annual subscription customers: Cross-Org Billing. See https://docs.atlas.mongodb.com/billing/#cross-organization-billing for more information.
With this capability you can move some Projects to other Organizations (this can be done without downtime via a purely logical backend move), giving you a loose-coupling with authorization-level isolation, but a shared billing subscription.