Ad-Hoc pivoting custom visual

Is there any custom visual available where as a developer you can can add a list of fields and measures and allow the user to basically use them in any manner they want in a pivot/matrix format within the report itself (not in Power BI Desktop) online. 

While dashboards and report solve 80-90% of the needs, there's always a 10% ad-hoc need that comes up and having a functionality like this will greatly help solve the final 10% problem without having to expose the whole data model or a perspective to the user that they then need to connect to separately from excel or have them download a data dump. 

The goal is give something within the report itself so they can play around with it if the standard views in the dashboard don't solve the need.