This question has no definitive answer. It is implied he can use the full power of the Rinnegan though with just his special one as every person in existence with a concentric circle eye with tomoes only have one of them(Kaguya, Madara, Sasuke, and the Holy Tree). That known, it wouldn't be possible for him to gain an extra Rinnegan without stealing someone elses. That means that his own special ability shouldn't be upgraded.
You're adding Madara's immortality into his Limbo features. It's not really a substitute for death because the shadow will always reflect back into the user and take any damage it received with it. That means if he weren't immortal and got stabbed in the heart, of course he could replace with a clone a live for a couple extra seconds; but as soon as the time limit is up, then Madara would die or get severly injured.
