I keep asking myself similar questions to the OP, though with slightly different routes.

It seems like Finnair might be an option for me in the near future due to the opening of their SIN route, so I'm wondering which OW FFP to use should I start flying with them.

BA seems like the natural choice if you can use an address in continental Europe, but if you only fly in Y then gaining status is next to impossible. Redemptions are apparently also tricky, with some routes showing little to no availability in premium classes for long stretches...

Just curious if apart from AA there are any other hidden treasures out there...