When did Kakashi become an Uchiha? Also, what do you mean Madara wasn't that strong back then? Madara's name alone was enough to make the Daimyos of all the five great nations agree to the first ever shinobi alliance.Furthermore, Madara non-rinnegan techs are powerful.As for all Uchiha getting different abilites when they "awaken their sharingan to a high enough level", that's bullshit.If that was the case, why does sasuke have the same abilities as Itachi? I already know you are going to used the bulls**t their brothers, but that argument is still flawed.Case in point, Madara, someone who died nearly a century ago has Susanoo, and so does Itachi and Sasuke.If it was true that when Uchiha "awaken their sharingan to a high enough level" that they get different abilities, then why would Itachi and Sasuke have Susanoo.The answer is clear, MS give you three abilities and those abilities are the same for all who awaken it.Of the MS abilities that we have seen Sasuke and Itachi used, Madara has used two of them, Susanoo and tsukuyomi during the battle.And if you don't think Madara used tsukuyomi, go back to the chapter when madara first started fighting and you will see him using genjutsu on one of the shinobi.The only thing that different with MS is when someone develops their own jutsu on top of the ones already given when you awaken it;Like Shisui Uchiha's Kotoamatsukami or Sasuke's Blaze Release.
TO YOU, It was stated in the Manga that every Mangekyo sharingan technique is different and created by it's user after acquiring it. Kakashi uses different MS techniques than Itachi and the same goes for Sasuke and Madara. We all know Kakashi is NOT an Uchiha. However, you are correct, every Sharingan user gains the ability to use Amaterasu, Susanoo, and Tsukuyomi after gaining the MS.
Kakashi explains that you can customize the genjutsus sometime before Part II and then again in Part II. Also the users' Susanoos differ between characters.