I have had my Squarestream trailer for six years now, acquiring it from my parents who were the original owners, Over that time made a few upgrades due to maintenance needs, and better technology available now that wasn't before, The first upgrade was a Progressive Dynamics PD4600 power converter and battery charger. The original B-W Charger overcharged the batteries if the shore power cord was connected to AC, shortening the battery life, Now the batteries stay charged in winter without being boiled to death. I was able to do the conversion myself as I am handy and understand electricity and electronics. Basically the new electronics fit into the shell of the old charging unit and the original breaker/ fuse panel is retained. I also installed installed a Surge guard Model 34520 RV power protection unit, to protect all my electronics inside the trailer, I installed the optional LED status display under the control panel on the cabinet side where you check the battery and tank capacities.
The 2nd upgrade were some chrome bullet hubs I found on Ebay that fit the center hole (3 1/8) of the stock white spoke wheels, inexpensive and a much better look than the cheap chrome plastic originals.
The third was replacing the furnace which had trouble igniting and since it was 24 years old I replaced it with an Atwood furnace. This necessitated enlarging the hole on the outside wall and re positioning the AC plug to above the rear wheel.
4th was The original water regulator failed, It is part of the fresh water inlet assembly hose bib. The closest replacement was nicer looking chromed though plastic like the original, however I had to make the hole in the exterior wall by about 1/2" wider than the original. I found a cup that had the correct diameter placed it over the hole to use it as a template marked the new hole with a pencil, then cut the hole with a dremmel cut off wheel. It worked very well. the threaded fitting to the PE tubing inside was the same as the old.
Fifth was the original radio casette stereo which is never great as RV factory installed equipment needed updating. I installed a Jensen AWM 970 which has a lot better tuner and can handle CDs DVDs connections to an ipod (but not iphone, alas) and mp3 capability. As this was 5 years ago, there are newer and better stereo units now. I had to cut the hole larger to accommodate the new unit, then have a cabinet maker friend make side panels for either side to cover up the old hole. It came out pretty good. It sounds good with the original speakers but plan to one day upgrade those as well.