Hmmm, this has been debated ad nauseum.
I'll give you the reader's digest version of what's been already discussed.
Generally, 2wd isn't for offroading, except desert truck type runs through the Baja, etc...where traction isn't the problem.
That said, there are plenty of mild trails and dirt paths, etc...where a 2wd drive can have fun...and a good driver can keep up with 4wd buddies.
Adding a rear locker is a nice equalizer, but not a panacea....as you stil get stuck/can't climb ledges, etc....as you can't unweight the rear to pull yourself up with the fronts, etc.
You ca maximize the rear traction with big aggressive tires, and the rear's can fit fatter meat than the fronts, as the rears do not also need to turn, etc...so a spare set of mounted play tires just for the rear is doable.
So - you will NEVER be able to do what a 4wd cn do. You CAN have fun though. If that's OK, then go the aggressive rear route (Locker/better tires) and a winch, to give your buddies a break from dragging your sorry ass along...to maximize what you have.
One conflict, you mention mud, which you want deep agressive tread for, and sand, which you want a less aggressive tread for to avoid digging/sinking....you'd have to have a different set of tires for each terrain, or just get BFG AT ko's or something in yet another compromise, etc.
One legged soccer players can still enjoy the game.
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- TJ
2001 Xterra '03 VG33, SE 5 spd, 305/70/16's, Revolvers, UBSkidderz, Doubled AAL's, 3"SL/2"BL, winch/bumpers, skids, sliders, OBA, Snorkel, pine stripes....
Friends don't let friends drive stock.
http://www.gifsoup.com/view/501230/tj-tackling-crawlers-ridge-o.gif