I'm finding it difficult to think of any AJX families living in Japan where at least one of the husband or wife are not Japanese. That's not to say there aren't but I can't think of any off the top of my head. Some guys have had their wives/girlfriends (not at the same time) staying in Japan for a long period but I think they normally come in on a tourist visa, as opposed to any sort of residential visa. I know nothing of the sponsorship schemes since I wouldn't subject my family to living in Japan.
ZED travel is open to your spouse/close family in accordance with the 'normal' industry standard. In other words, wife, kids, parents etc bit not your uncle Bob.
Medical depends on which contract company you use. Crew have got the best medical package and it is worth prioritising them if you apply because that package is worth a lot. It includes your family and everyone I've spoken to who has cause to use it has been impressed. Not so, Parc. Their use if BUPA Global does the job most of the time but there are plenty of horror stories where guys are having to pay bills themselves and then having to chase BUPA for non-payment etc. NOT what you need when you're off sick. Parc also has an 'excess' payment of GBP200/year and you have to pay extra if you want to include family. It is a vastly inferior package to Crew.
Nothing has changed really with upgrades. They're still assessing at around the 3.5 year mark and slotting in courses shortly thereafter. It doesn't seem to worry them being overborne by captains and there's no specific strategy to split 50/50. Being able to fly captain/captain actually allows them flexibility in having more 4 stripes than 3. I think it will be at least 3 years (possibly more) in the seat before we see any FOs go from right to left on the 787. I don't think ANA Mainline yet have a 787 upgrade program so we'll really be behind the curve on that score. Not that it will concern new joiners for the time being.....maybe in 7 years or so
.........maybe