<i>Sorry, BA, but we're both looking into Lufthansa or KLM for our flights to Oslo from now on.</i>

Good God, no. Not Lufthansa. Their business class is pretty much inferior to BA in every single way. Plus, connecting in FRA stinks. BA may be underwhelming, but Lufthansa is not the answer.

I would also put KLM behind BA. Maybe a Delta flight connecting to KLM would work, but KLM's long-haul business class is quite weak.