Okay, brain storming, not necessarily good as I am waiting for coffee to brew but... What about treating stained glass as a mix of the matte translucent (allowing for the needed texture map) and the either architectural or rough glass (to help simulate the imperfections that make stained glass unique.  I don't quite get how the mix works yet, setting up the two (or more) materials I get.  Bleh I'll figure it out.

Yay!  Robyn took a play break. ;) 

Going to go look at the site as soon as I have coffee in my hand and can think past... Cooooffffffffffffffffeeeeeeeeeee......