Yes, that will work pretty well. Not sure the app will accept all possible FFP numbers but from what I know it just pushes the number to the Amadeus Check-In system which should valid the number. So it should work with the majority of FFPs. Certainly it supports the EuroBonus scheme.

The only thing you're giving up is the famous strictly enforced priority boarding in SAS hubs

But by any chance they would call out Gold priority boarding first you can still flash the card.