Hi Marco,
If you are using MII 15.0 then you could use Self Service Composition Environment(SSCE) for dashboard creation. Visualization of almost all MII Objects are supported (be it QueryTemplates, KPI/ MDO/PIC tag objects etc)
Hence with 15.0 you could either create an MDO Query in Select mode or directly MDO object and visualize it as UI5 table/chart. There by you don't have to be worried about the service to give you data.
Hope this helps!
Thanks and Best Regards,
Ria