Composite models when connected to AS models (PBI datasets and Azure Analysis Services)

Being able connect to multiple data sources including live connections to live SSAS cubes (both multi dimensional and tabular) is in my opinion one of the most critical features currently missing from PBI. In a large organization where data and insights are available in many SSAS cubes this features would be like having the "holy grail" to enable virtual integration without having to rebuild measures or creating complex and unwarranted physical data integration steps.