Not news to you...but you can always throw the compressor in later...although it is easier to connect the air-line at the time you are reinstalling the diff.
FYI: You surely have read about the spat of 100 front diff failures over in the 80vs100 thread. FYI: I ran my '99 without the ARB for over a year without incident (with sliders, front/rear bumpers, drawer setup...i.e. lots of extra weight/load). Most of the miles I drove were on varied surfaces including dirt, mud, rock, snow, ice with over 50% of my travels being off-road and on trails similar to what's between here and VC..with 33" MT/R's with the CDL and rear locker activated on many of those trails. I was aware of the weakness...and used the skinny pedal accordingly. However only you can calc the risk/reward equation as it relates to this

.