That's the thing... I get the feeling that at least part of Shunsui's laziness is an affectation, look at his fight with Starrk, he bitched and moaned, procrastinated and even pretended to be hurt so he could skip the fight...
But once it started he was anything but lazy and as such finished the fight with comparative ease. I think Shunsui uses his lazy persona in an attempt to fool people into thinking he's less of a badass than he really is.
I do agree that whatever his Bankai is, it's going to be a TOTAL mindfuck. I'm still sticking to my theory earlier that the whole "Childrens games" thing from his Zanpaktou is actually a side effect and the real power is the imposition of his Zanpaktou's will on anything in the radius, thus his Bankai is going to be the ability to impose HIS will on the surroundings and anyone or anything is the area.
Also, much like Ichigo getting a bow instead of a Zanpaktou, Aizen coming back for the last battle, especially if he sides with the Shinigami, would be a deal breaker for me. Aizen had his time in the light, but now it's over and his arc is DONE, if he returns (outside of this flashback arc obviously
) Then I'm out.