Here let me save you a YEAR of pain, balancing and people screaming at you. Covenants have about as much choice as when you told players Azerite gear had choice.
If you pick the wrong Covenant then you have volunteered to gimp your class. Only way is to make the abilities you get be pointless which means they will NEVER BE USED.
Just take my word right now and scrap this idea. Go a different direction while you have time. Please open it up more, allow some type of choice system because if I go the wrong Covenant you might be stuck a good Prot tank but trash Ret abilities.
Just come on guys do not repeat BFA. This has red flags all over it.
(Info based on Ion dev panel he is doing and how I am interpretating it.)
Update 4/7/2020: I TOLD YOU IN NOVEMBER!