Hi,
In a dashboard I think it is feasable, even if I never tried.
I don't know what will be the behavior if you try to link it to a map (it may crash).
You can try an let us know if it works.
You will probably have to create a view on the database that does an outer join, so you have the cartesian product on the data published.
Then publish the view as a layer on GeoServer and create the dashboard using the layer published.