Isolating Groups (not only data they can see)

Hello there,
We have been trying out Metabase at our company and are thinking of using it as a platform to sell our data services so each of our company customers can have their own capability for creating their own Questions/Dashboards.
I have already understand how to somewhat (isolate) data with User Groups and Dashboards with Collections, but it would be nice to have an absolute isolation, including from Feeds. Even this “collections” isolation isn’t totally correct as there are some dangers a user forgets to add the question to a Collection and, even if other User Groups don’t have access to that data table, it will be visible to them…
Otherwise, it would be nice that even if the Dashboards are chosen to have a “public link”, they don’t necessarily appear in the Feed.
Since I couldn’t find a way to do this, before posting on “feature requests” I’m posting this on Get Help first.
Anyone has some ideas on how to achieve this “complete” isolation between User groups?