I'm a big advocate of the factory cooling system on an XJ. I have had a number of XJ's over the years, and have 2 that are on 1 ton axles 40" tires, etc. Both run OEM style cooling systems and have for years (mechanical fan, shroud, factory style radiator, OEM electric fan, OEM temp thermostat). Both of these Jeeps see way more highway use than trail use too. I live in East TN where the temperature and humidity in the summer can get pretty nasty. I can wheel whatever trails I want all day with the A/C on and never have an overheating issue. I've also wheeled in Moab and Sand Hollow in the dead of summer as well with no issues.
Most of the issues I see with XJ's overheating come from people who've had failed/failing parts over the years and try to "upgrade" those parts when in reality, they're only making their situation worse.
I am also a big fan of Detroit lockers. I run them on both Jeeps and they've been incredibly reliable. It's almost every ride, we're stopping and waiting for someone to repair a ARB locker for some reason. Melted air line, faulty wiring, leaking seal in the diff, etc. The Detroit is simple. It works. Has great road manners as well.