SAP BW Variables in Direct Query - make available to report user

When connecting to SAP BW in direct query mode it is possible to change report parameters (such as the currency or the date period) in the variables windows. However after publishing the report to powerbi.com it is not possible to change the value except by changing the pbix-file and re-uploading the file.

The most user-friendly option would be to allow accessing the variables from within Power BI - e.g. by providing something similar to a "disconnected slicer" table. For example when using the currency as variables it would be great if another table "Currency" would show up in the field list. If the user would select one currency (e.g. by using the table as slicer), the direct query connection should pass that variable to BW.

Alternatively if this is not doable it should be possible to change the variables via the dataset api (similar to parameters).