Your build is coming along really well, and the amount of effort you are likely putting into it is clear.
As a model truck building and detailing enthusiast, I understand and agree with the points you raise about the kit, or others like it. I generally like working with PE, but have come across kits where it is ridiculously thin, and to your observation, makes it almost more work than it is worth. And, I suppose the same goes for tediously complicated suspension/driveline assemblies (the Bronco 6x6 MPCV coming to mind here!).
I think the material used for PE makes a huge difference in how the parts work and look, reminding me of my favorite, being the Aber PE sets for T-55s. As ridiculously high count of small and complicated parts, but, they work well and look good once installed, with most actually looking better than the parts provided in the kit, even some on the MiniArt versions.
Like the gussets you have installed, were they really needed to be made from PE? and if so, why did they use such thin material? As ‘simple’ as they appear, my bet is they were harder than someone might guess to install - not just gluing them in, but keeping the material flat, and the edges flush or perpendicular to whatever they were being attached to, or installed next to. I wonder why they didn’t make them in plastic? and instead make the splash guards next to the engine in PE? which look too thick. And, as a suspension enthusiast, I’m not sure how much I would love making up multiple sets of scale U joints! I know, gripe, gripe. gripe!

Coincidentally, I’ve been working on a few old AMT kits lately, and can report with clarity that the plastic shapes called U joints…yeah, do not look as good as yours do, or much like U joints! At all! Many of the parts share this attribute, as they look vaguely similar to the the desired part, but need some work to get them looking better. And, locating pins and clear instructions would help!
So, I will watch you bravely march, or in this case, drive forward with this interesting build!
Cheers
Nick 