Looking at it I would suggest just quilting in black thread around the stained glass in the middle of the sashing. If the batting spacing allows I'd be inclined to just go around each unit made up of 3 small squares with 3 long bars.
Or you could so SID around those units. Either way, the units would look like their own stained window.
I'm with you less is better(and fluffier)
BTW I love your quilt!