O2: what do it do? (O2 delete?)

So dumb question, but with my de-cat causing O2 CEL is there any reason to even have a downstream O2 sensor? I'm gonna mask the code anyway, so can the upstream act solo, and the downstream be essentially deleted without causing the car to limp? I suspect my downstream unit is toast, so if I can just unplug it without ill effect I'll do so.