If you do it well.....and don't compromise the glass....I don't think so.

I'm not sure - but the framing looks to be original showing that the window was removed intact from a building with aged paint, giving some authenticity to antiquity. With a spiffed up paint job, it won't look any different from stained glass that was made yesterday.

It's a beautiful piece no matter what you decide.

I had a reason to see to the repair of one panel of a large stained glass window in our church. New glass looks different from old glass. Amazingly there were some sheets of the original glass in the attic in the color of the largest broken area and the man who did the repair had some old glass in almost the same color as the brown that was broken.
Those windows have been re-camed, the inside frames restained and the outside frames repainted many times. I don't think it has lessened their value.
I think it depends if you are looking at the art value of the stained glass....or the decorative value of the stained glass in the frame.

Thanks so much