I have noted some of the same problems with the fiberglass quality that you have, but have learned just barely enough about repairs so I don't panic. Something I find bewildering is the apparent variety of molds that have been used, sometimes even in units made in the same year.
The mismatched shells which show up most glaringly around the front and rear windows
are disturbing to me, but I have come to realize that in my unit there is no real practical penalty to this, so I have installed some curtains to cover this up. I have plans for some woodworking to complete the job underneath the window and over the front table.
Over the last 10+ years I have made modifications too numerous to remember, mostly because the basic concept and layout of the trailer fits us to a tee and we plan to keep it, as in "making it a hobby."
I have enjoyed learning to deal with one aspect or another and there is probably no end to this (I hope). As late as yesterday I finally cleaned out the weep holes for a couple of windows
because a little water had entered during heavy rain. In the process it became clear to me the way the drain system is designed, etc. I needed to install a missing "vent guide" to keep a window firmly against the edge of the frame and in the process finally found a good supplier of Hehr windows
and parts. Little by little it has become possible to improve and maintain the unit, so I'm happy.