I think rather then have the random spawns, instead demon lord perk removes the timer on Abyssal armour, weapons, summoned Mount and the Abyssal call demon.
Comparing corrupted strength, the build allows for permanent damage increase without casting a spell or needing any gathering of resources other then the initial soul drain.
With demon lord perk allowing for permanent demon summon you get to keep the defense of the abyssal Armour which makes sense because you have all that authority to 20. You would only be able to summon one Horse, demon pet at a time, the abilities are already in the game, you would just be able to keep them with the updated perk.
I feel it would make corrupted authority much more fun, and you would use abilities that are under used, and also more competitive in pvp.