Ding! :)

Or do like my kettle wife and fly WN any time she's flying by herself... I'll never understand women.

I don't think it's been asked, but how often would the PM be flying without the FO, how often together, and how ofter would the FO be flying without the PM?

For me (AA MVPG, kettle wife), the ratio is 10:1 on segments and 5:1 on miles, with 95% of my flights for business and 100% of hers for leisure... although it doesn't apply directly because my status is BIS, and this is going to sound a bit selfish, I don't think I would take a lower tier of status and associated degradation in benefits (and IROPS protection) for 60 segments to boost her level of benefits for 6 segments. The ratios may make it a different story for the OP. The would also play a big role (to me) in paying for multiple Reserve cards vs one and a couple of lounge day passes for when the FO is flying alone. Specifically, and this will depend a lot on routes and home-base, but upgrades as a GM for me last year were pretty non-existent, but many times I was close enough that I probably would have got it as a PM. In my case, the lack of upgrades as GM pushed me to AS, allowing me to be price-agnostic between DL and AA on shorter-trips and get guaranteed upgrades ahead of time on TCONs (luckily SEA is my most frequent west-coast destination)... that's specific to my situation, but it shows that for me they were few and far between enough that I could take fairly drastic action with minimal impact on my level of service on DL segments.

I doubt the OP is in the same specific situation as me, but if their split in PM/FO flying is similar, I would think PM would make their life easier during frequent business travel while FO wouldn't be a huge slight to the significant other on leisure travel. If their splits in travel are different, my whole justification goes up in smoke.

Well said - this was exactly my thought.

Of course, everybody will need to figure out their own ratios and make their own call based on that. For me and my wife, getting her status when there were other things possible just didn't make sense.

I think what makes the most sense for us is the PM/FO combo. We will be using our miles mostly for our son, who has no status and may be traveling with 1-2 week's notice RT from WAS-DTW. The waived award change fees would be helpful.
I'm thinking our plan could be to alternate which one of us is PM/FO each year, thereby being able to use both of our miles (every other year) and get the award redeposit fee waived on the PM's miles. Any faults in this plan?