I've been thinking this to death tonight, so I'm just appealing to the collective wisdom of the interweb to try and get an outsider perspective here.... I find it much easier to logically analyze others' trips than my own, so hoping that's the case for others as well.

So here are the balances I'm working with trying to put this together:
ANA: 400k+
UR: 300k+ (though my gravy train for earning ~40k/month just dried up)
UA: 30k
US: 135k
AA: 75k (with 60k on the way, so generally prefer to not use and build a critical mass here)
AS: 69k
SPG: 98k (emergency only, really ... prefer not to transfer except maybe 1k to Alaska to make 70)
BA: 86k (planning on earning companion pass this year)
MR: ~10k but ability to advance 60k+15k (2 diff accounts)

Obviously, my strong preference is to spend the ANA miles as they're probably the least valuable (except maybe BA, though I will be getting the companion pass this year so...) and they expire even with account activity...

The trip plan is IAD-AMS-[somewhere in Europe with beaches... thinking NCE or PMI, but absolutely open to suggestions]-IAD

Also open to beach destination first should availability look better for that, but don't love the idea since we're generally beach people and I don't want to regret leaving... prefer looking forward.

We're currently booked IAD-AMS-IAD on UA C for 68k per person ... great deal, I know, but I've got more miles than I have time and now we want to add a trip to somewhere warm. We don't have to change the trip at all, and won't if it requires killing a whole day in transit, but we're already in Europe, so may as well spend a few extra days.

My plan now is to wait until 10-14 days out and try to book with ANA miles:
IAD-FRA/MUC (LH F)
FRA/MUC-AMS (LH C/Y...who cares)
AMS-*A hub-NCE (for example)

NCE-FRA/MUC/ZRH/etc -- ONLY IF NEEDED TO POSITION TO LARGER CITY/AIRPORT FOR FLIGHT ON OTHER ALLIANCE ON RETURN
or
throwaway segment like YUL-BOS sometime next year to comply with ANA rules if we don't return home on the ANA ticket

That should be 90k ANA pp in F which is a bit steep but it's basically 2-3 one ways, so I can't complain, really... fuel surcharges are no problem as they are a deductible expense in this case. That said, I've got more ANA than I know what to do with, so I'd honestly rather "overpay" a bit with them than burn more valuable miles/points.

Then the return to IAD would EITHER be something in *A C/F if available at time of booking since ANA doesn't allow changes, and I wouldn't want to lose out on the LH F availability by waiting once it opens up.

or, if nothing in a premium class on *A opens up, then:

use BA/AA/AS for 1 way home on BA/AA ... whatever is available, so most likely BA

If nothing does end up opening up on LH (would be surprising IME) then we just keep the r/t to AMS and come home a little early to a very happy dog...

Thoughts?

More efficient way to do this while still protecting more valuable balances to an extent?