I believe there was some discussion of Terry's Vizard plot, though that would be difficult for the lower level characters to participate in.

The first mention of the lower level shinigami appears to be Arc 3 in the planning stages (Michiko, Kasanip, Controlled Shinigami, Samsara) where I mentioned that the lower level Shinigami could enter there, trying to figure out what on earth is going on.

Other then that, I can't recall much.