They will eventually explain why Kakashi has a Mangekyo, they'll also explain why his is so drastically different. They'll explain why Madara is immortal, and why he can phase, and teleport, and all that stuff, we just have to wait. Stop trying to use that as a basis for other things. The rules for the Sharingan are known.
1. Regular Sharingan varies in power from 1, to 3 dots, 3 being the most powerful.
2. Dots and designs of each Sharingan are different.
3. To get the Mangekyo, you must take someone's eyes, it's supposed to be brother, be Itachi took his best friends(who could be seen as a brother) That could've been the only exception besides Sasuke.
4. To get the Eternal Mangekyo, you must take your brother's eyes, otherwise you'll just have Mangekyo, and eventually go blind, probably losing all Sharingan related abilities in the process.
5. Sharingan eyes can be transplanted, but they will always be on, so they must be covered to conserve energy, because the drain is far larger on a non Uchiha.
I could keep going.