Build the plane you want, but recognize that deviations from standard frequently become liabilities at re-sale time. If you never plan to sell, this isn't a consideration.
That said:
- That section of the airframe (the surface that includes the plexi and the sheet aluminum frame around it) does appear to be a flat wrap. At least, it sure looks like it on mine. If so, it should be possible to wrap a uniform sheet in the same location.
- Echo the concerns about where you'd put the door. Below the top longeron would require a structural frame that distributes the load carried by that panel instead. And with the tail down, that panel is quite low which might be awkward to access.
- Above the longeron and you'll have to reach down into the space... I don't think it would be that awkward, you'll usually park with the flaps down anyway which lets you get closer. And on the -6 the tail is lower which helps too.
Still: I'm *always* using the window behind the seat to look around. Taxiing, manoeuvring, formation, aerobatics, etc. More window is better, IMO.