Nice effort, but there are some flaws:
You noted how the panel focused on Madara's eye when he used limbo and claimed that this is how MS works, but re-read the most recent chapter of Gaiden. The panel homed in on Sasuke's rinnegan when Sasuke used amenotejikara.
Also, you are wrong in saying that the rinnegan doesn't have unique techniques to certain users and here is why:
When Madara was analyzing Sasuke's amenotejikara, he said stuff like "So that is his left eye's power" and "Sasuke, I think I am finally starting to understand your left eye's power". The fact that Madara described it as Sasuke's power (despite the fact that he himself has the rinnegan) suggests that Madara does not have amenotejikara and that the jutsu is unique to Sasuke. We know that Sasuke did not have a weaker version of this as one of his EMS techniques because we have seen all of his EMS techniques and they are amaterasu, blaze release, and susanoo. Therefore, rinnegan does have unique jutsus that can be used by the original awakener of the eyes.