And Byakuya was so confused when Ichigo bankai was "small"...
Anyway, seriously WTF is Unohana doing? This is ridiculous. Isn't she suppose to be strong one since she's one of the oldest?
And what are they waiting for with Yama? There is this second dude beside buck beard so why won't HE steal Yama-ji bankai? Yes, we know Genryusai 'll lose you may proceed with it, you don't have to present him with "cool" death while he is in his full power.
EDIT: And one more thing.
Vaizards.
They have their masks aside from their bankais. That's some serious power boost right there. So, why won't they use them? Why don't force THEM to lost their Bankai on purpose since they have the advantage of the masks? Imagine Matsumoto shouting to one of them: "Hey, you, Kensei, since your bankai is useless and you lost with some random arrancar dude with it, let it out! We will see what these guys are upt to! You still have your mask!"