It is already possible to allow the user to select which metric is used in charts via a switch function. What you cannot do is allow the user to select from a list of fields in a slicer that will change the axis of a chart to dynamically change to that field. I know you can use drill-down to do this but that functionality is not natural to users that don't use Power BI often (like executives). In Tableau you can point to measures or dimensions in their version of a switch function and Power BI should be able to do the same.