These are not mods but just ideas that work well.
That huge bathroom closet in the 22FB needed something to fill it up:
Note - still plenty of space underneath for towels and such.
My trailer has a 90 gallon tank and I don't need that much water on shorter trips - the trailer's water gauge is pretty vauge - so I got a water flow meter - good upto 1/10 of gallon. (Not trying to sell Ultra Light Beer just used for perspective)
Where to put those large antigravity chairs?? Tried several locations but none made me happy - always in the way - I finally figured out I could stick them under the couch.