Different users groups see same reports but using different connection strings

In our app we want to have separate groups of users who see their own data, but all groups are using a consistent set of reports/dashboards (using Direct Query) to do so. So the "code" is shared across all groups but the "data" is per-group.

Unfortunately in PowerBI it seems the connection strings are burnt into the data sets that the reports link to.

So our workaround is to create a separate workspace for every group of users, and copy dozens of reports/dashboards into them all. There being no API for doing this, we had to write it - it's error prone, you apparently can't replace or delete a dashboard via the API (I suggested this in December 2017) so we have to embed version numbers in their names... Also it takes a very long time to perform this copy per group, so as the number of reports and groups increases our automated deployment can take literally hours, almost all of which is PowerBI.

It would be far better if we could once upload the definition of the set of reports/dashboards to a workspace, and then separately maintain the different connection strings to be used by the different groups of users. Then to update the report definitions we just re-upload them to one workspace and they immediately become the new report definitions for the users across all the groups.

One possible approach would be for one workspace to be able to include the content of another but override the connection strings. This would allow each group to add custom reports if required.