I'm trying to grasp what you're wanting to do here. So you want to remove all windows with there frames and overlay the whole upper area with like a dark polycarbonate material? Sounds like you are after a sleek look and feel correct? It's nice to be able to open windows but I guess with air on it wouldn't matter so much. There are several owners that have accomplished quite a bit of modernization with paint. Others have replaced old windows with more modern.
Here are a couple of updated coaches.
http://www.luxurycoachlifestyle.com/...int-job-2.html
http://www.luxurycoachlifestyle.com/forum/upgrading-your-motor-coach/2551-before-after-1988-newell-body-paint-same-lines-modern-colors.html
http://www.luxurycoachlifestyle.com/...my-brotha.html