fdresq4- While I do like the KSG, it's generally not available OTC and IME it's really only good with 4-6 layers (and the more the better).
For a single-coat product I'd go with FK1000P, hands down. But it's not OTC either.
So that brings us back to Collinite 476S, second best (after the FK1000P) with only one coat, at least IME. 845 is nice, and *very* trim-friendly, but it doesn't last like 476S and it really needs more than one coat.
RVM- redoing/adding clearcoat is problematic at best and yeah...very big/expensive job that isn't usually feasible (basically repainting the car without using the "basecoat" part of the basecoat/clearcoat system. Don't go there.
The coating approach is fine, but yeah, gotta do the prep right. Either DIY it or have a (GOOD) pro detailer do it (NOT a body/paint shop).
Eh...for your off-roading vehicle, and the time/effort I think you want to put into this, I'd probably go with the DuraGloss. I mean, really...how involved do you want to get with this whole thing?