Combine on-prem Tabular with new PowerPivot data

I would love to see the option of online connecting to existing SSAS cubes (Tabular/MultiDimensional), and mash up with my own data in PowerPivot. If i have a large enterprise tabular cube, which I want to combine with my own data. I would like to avoid having to import data from the Tabular cube, just connect online. The purpose is to give self-service users an option to extend on enterprise models, without having to import data already existing in the enterprise Tabular cube.