I can't think of a way to eliminate the CEL for the rear O2 sensors. They wanna see something burning, or what's the point of them there.
Unfortunately this part I have little experience in (cold air, cat delete).
From what I've read here, the best performance mod for the V6 is that raised air intake spacer.
Some have installed the Doug Thorley (??) headers. Probably search what that result achieved. I think those delete the front cats, and go along with what you are thinking to do.