Yeah, but I think the Wall isn't necessarily only for playing ability...it is, in no small part, reserved for guys who were good players, but also represented the franchise well. I am in no way making the argument that Hansen was a better player than Bennett (Biscquit is one of my all-time favorites), just that the Bills (Wilson?) may not feel that he meets the same criteria that Hansen meets. Also, I think you are kind or downplaying how good Hansen was. He got better and better as his career went on, as I recall.
I suspect Ruben Brown may make the WOF at some point too...and Moorman. Ruben had his one run in with a O-line coach in his final season, but was a great (very underrated by Bills fan) player, and a good representitive for the franchise.
I would also argue that maybe your guy, Metzelaars could go up on the Wall...but they will eventually run out of wall space!