I looked at this when contemplating our own trailer. To me, it made a lot of sense as a vent for the cooktop, a pass through, and as just extra light. I'm sure that Oliver just said no, but I never pushed it because I couldn't figure out what to do with the inside. That is, you'd want the same window treatment as the rest of the trailer, and those things are thick enough to really encroach on the counter space and especially the cooktop.
As a retrofit, I think it would be possible but obviously difficult, especially since you'd have to work around the existing counter.
I think it would have been a waste anyway, since it wouldn't have worked for the pass through or vent like I was thinking. Since I grill under the awning, we learned pretty quickly that all the windows on that side need to stay closed while cooking dinner. That, or disable the smoke detector ;) .