a few questions to ask you: will Mrs be flying as much as 100K status miles (aka FOP) for her status? actually, you only need 80K for JGC Premier as I'd assume you would join JGC after you obtain 50K FOP (50%+ JL metal). main
difference being domestic benefits...

assuming that she would obtain JGCP:

2) is irrelevant so you can get other gifts instead. like 10x2000yen vouchers + domestic F coupons that I got

3) unless you want the few Japan based member benefit, i think being an overseas member is better. (main difference being the ability to use the japanese JAL CC as domestic BP) overseas member doesnt need to pay CC annual fees, but only a membership fee of 5000 JL Miles a year or by earning 25000 FOP.

4) since there's quite a cost to join, i didnt think much about it yet. but the redeemable miles is what will be pooled, not FOP/status miles.

overall speaking, since japanese CC has a terrible earn rate (typically 100 yen/mile) i would think of using a good earning foreign card in japan instead.