From what I've seen already:
1. Yes the WJ's are 5x5, easy to redrill though.
2. The WJ caliper brackets have a 3" dia. center hole, haven't checked the bolt pattern yet.
3. The WJ rotors are deeper than ZJ, however it appears that the brackets are offset to make up the difference. If the axel shafts and housings are the same length then this should work.
I was just wondering if I would be the first to try this swap. My pinion bearings are starting to make noise, so I'll rebuilding the axle very shortly. While it's apart I'll find out. Hopefully it'll work and then I can start a search for WJ outers.