MIGXdb Grid - Sort by Arbitrary Column?

I've got a grid that uses several renderers to display underlying data in a recognizable form—a couple of which render certain fields from a stored resource ID. I'm wondering if there's a way to sort on what's rendered instead of the actual data value. I know in a regular (non-db) migx you can create arbitrary columns to do certain things (including I suspect creating an alternate sorting column) but this doesn't seem possible when using migxdb. Has anyone tried to implement something like this with success, ideally using an already built-in method?