I've been running a 3" BB for 0ver 10 years, some 300,000kms, on two trucks. There are no problems with the front coming loose ever, even at full droop, even with the shocks and swaybar off, because the OEM lower control arms prevent the diff from dropping far enough. In addition, the front bumpstop post is over 5" long, plus the steel bumpstop socket os bolted on to the end of that. When you put BBs in the front, it is always under at least a bit of compression, even under full droop, because there is less "room" for the spring than before! In other words, a BB actually makes the springs harder to remove, so harder to have "fall out." Where did this myth start??
In the rear, there may be some concern. The spring is located by a much shorter post. The solution for those who want a 3" BB is to install a piece of exhaust tubing over the post and then install the suspension. I have not done this, and I wouldn't bother, because you can get the same 3" of lift from a Front to Rear swap using I6 ZJ springs. No problems with the spring ever moving, and used springs are cheaper than BBs in my areas. Actually though, even with the swaybar and shocks off, the springs are hard to get in with a 2" BB. I can't imagine they'd be able to move (especially with the swaybar and shocks on!), because with the OEM LCAs, the rear springs are ALWAYS under pressure, even at full droop.
In either case, you will not have any trouble with articulation. Check out my Public Profile pic and you'll see my 31s rubbing the top of the spring post, even with the 3" BB. I've extended the front bumpstops 1" (a simple aluminum puck) and the rear 1.5" (square steel tubing, actually from a RE kit).
You will have no issues with front end geometry, as you can adjust the caster so easily on the ZJ.
You will definitely have vibration issues with the stock rear suspension, but they can be "reduced" with a transfer case drop. Or hopefully removed with adjustable lower control arms.
There is NO CHANGE in ride quality with a BB (another weird myth???) because you're using the same springs!!