I don't know how important that XT shifter is TBH. I would not bother for multi-up-shifts alone.Thanks so much for all your thoughts on the fork... I will likely stick with SLX, and plan to make upgrades in the future. Definitely the XT shifter, and eventually much higher end fork. The SLX seems pretty solid overall otherwise.
The most important upgrade for the TJ - IMHO - are better brakes, not so much for power, as much as ease of one-finger breaking + modulation. The new Deore & SLX brakes, 2 or 4 pot, are excellent from my experience (M7120).
And once you have the brakes and you are in your splurging mood, you might want to get a matching i-Spec EV shifter (XT or not) and i-spec EV dropper lever (MT500 or MT800, both great, and unless you are after colors, as good if not better than the more expensive PNW, Wolftooth etc equivalents. Really like that the Shimanos are spring loaded and return perfectly). Again, not needed as much as the brakes, but at least this way you are getting a cleaner and easier to configure cockpit, on top of better tactile feel and/or multishift (which is nice to have, but not nearly as important going to higher gears IMHO).