Well your goal 4 to 6" is not un-do-able (is that even a real word?)
Well heres what you have to work with at this time:
SuspensionCalmini 2.5" Nice system and will take all you can through at it. Lots of flex. Rough ride are so people say (I don't think so)
RRO 2"+or- do to weight of xl-7 Sorter ride not as much flex reuses stock a-arms (camber issuse) and no adjustment forthe rear track bar.
Body liftsRRO-- None as of right now working on 2" BD lift system
Calmini-- none as of right now they do have a 3" system just not for sale :-/
Bigballsoffroad 3" system (based out of AU)
Others- - 4 to 5" systems that I have seen but won't tell you about do to the fact that any thing over 3" is risky.
Tire SizesStock 225/70/16=28"
2.5" 245/75/16 31" or may be 235/85/16???
2.5"+3" body 265/75/16 33" not 100% on this one
Locker, ectNone as right now how ever I did here that ARB may have something in the works
GearsNo real option for R&P if you have an A/T (5.12r&p)
if you have a M/T you can up grade to the 5.12's
T-caseHave heard that xl's have differnt gears from GV's so this may be an issuse???
Calmini
RRO
Bigballsoffroad