Look at Blut Aus Nord, Nokturnal Mortum. Those are keyboards done well...But if Opeth decides to have crap like Children of Bodom keyboards with random solos I will go on a rampage and kill alot of people.
CoB keyboardist is damn good imo. Ofcourse that style of keyboarding would only suit a melodic death band. It doesn't add any creepy ambience to the music. I wouldn't mind hearing an opeth song done with some added violins ala MDB.
violins would be nice...as would cello/viola...
they would have to be legitimate though, NO samples (unless done on a sufficiently dated mellotron with that perfect vintage sound)