Allan a Fsus2+added6th = F G C D while a Bb69/F = Bb D F G C so wouldn't a Bb69 add a Bb somewhere in the chord? I have always assumed that it would or should but maybe I'm wrong.
I see where you're coming from. I thought the Fsus implied a sus4 (Bb) as well as the G and C.
Perhaps you're right. In that case i would say Gsus/F would be right after all.
Alan