Strategic Group summary rollup - Enable summarizing by something other than "Site"

There is a function where, for example, at the bottom of the strategic group administration page, you can set the number of devices per business workflow before summarizing by Site.

Our site usage is defined by customers and often the "Site" is meaningless to us from a business perspective. It would be mega helpful if we could define this rollup so it rolls up by category or device type or something user definable, essentially anything other than site.