Did not go from a 5th wheel but did go from a TT to a PUP for many of the same reasons as you noted. For us it was just a non use issue as our kids are getting older and keep us busy running around.
I missed the bathroom the most, we have a porta potty and while that's ok its just not the same has having the real McCoy with a shower.
My second idea was to get an old 18-20' TT gut it and do a makeover. I'm a wood worker/welder and just enjoy working with my hands after pushing a pin all day. I still may pick one up, it not going to be a crazy leaker but something that has something left of it.