Azure Analysis Services & External users

Hi all,

We're currently building our BI module connected to our ERP solution, that we want to deploy towards our customers, and we face a challenge. 

Here is how we proceed today to build the reports and deploy it: 

1. Building the Model on Visual Studio (Tables relations, new columns) and deploying the Model on Azure Analysis Services
2. We create a workspace for each customer at app.powerbi.com
3. With Power BI Desktop, we connect to the Model on AAS and we build the reports (new measures, vizualisations) and we deploy it on the workspace created for the customer

Now the challenge is to open accesses to these reports (viewer, contributor or member) to external users (different mail servers than ours). 

Our testing showed that it works if we add the user under "Analysis Services Admins", and we share the reports on the workspace, the external user can access it, but we've seen that the user has also access to all other Models on AAS, for other customers as well. 

If we don't add the users on Admins, but only share the report or workspace, they get an error message saying that they don't have access to the AAS model. 

The questions are:

• Is our deployment approach as described the best way (we want to use AAS instead of Power BI Premium for cost-flexibility)?
• How to open accesses to external users?

Thank you very much for your help.