I don't think the power upgrade makes him OP or a Mary Sue especially since the story has put him in a very bad situation. I don't think the king of the dead is no more over the top then world breaker, extremis, etc, etc.
As far as why, I believe that this threat is a very old and I think BP will be given insight from his ancestors that his peers won't be hip to.
But I guess the tech in itself is an upgrade. In the first issue of NA he demonstrated a force field and teleportation.
Course, he hasn't used any of that since then.
As far as upgrades go, I'd personally be cool if they just brought back all the gear that Priest introduced, but which mostly vanished in Hudlin's run. Energy daggers were cool.