composite models when connected to Power BI dataset

Similar to another request that is posted, but this is specifically talking about composite models using a Power BI dataset

As a large enterprise we are trying to make live easier for our end users by building a set of enterprise models with pre-approved content. However we also have a number of business users who like to expand upon that with typically excel data sources.

There are a few main requirements:
- We want to have the central datasets in a central workspace and business users should be able to re-use them (this is coming)
- Row level security needs to be applied for the developers. We have a global report, typically developers at region level and end users and country level. Developers should only see their region
- Extra datasets need to be added. At the start an excel file will do since most business users tend to use that

More than happy to do a call and expand upon this. For now we have 800 power bi users and growing fast within the company