I thought I read in another post that you wanted to wheel it stockish for a while and just add armor for protection. I've never had a sectable in any of my Jeeps. I've run Aussies and Lockrights in the front axles on a couple of them and I've had a Lockright, a spool and 2 welded rear axles. I would not suggest welded rear axles, especially in a TJ. It tears the control arm bushings up and really throws it around a lot pulling into parking spots on cement. My TJ has a D44 rear and will have a Detroit installed by the end of next week.
I love the option of selectable lockers, but I've never been able to come up with the money to put one in and I've never had a problem with the lunchbox lockers. I drove my current TJ through a winter with a welded rear end and didn't crash it, which surprised me since it was dangerous a couple times. If you go with a Detroit or lunchbox locker you just have to taylor your driving style a little bit and you'll be fine. I would look for a D44 out of a TJ to throw in your TJ. If you get a later one you can get disc brakes and all of that also.