I like most of your story idea.
I'll probably add some twist (golden axe being evil being or Death Adder turned out to be Ax Battler's long lost brother) but of course if it's a twist it shouldn't be spoiled either.
The thing is if TMNT Shredder's Revenge is a success, there is a chance that Golden Axe Remake would be happened through them.
If it's happened, I bet the story would be as simple as SOR4. Just regular good vs evil story.
Well, I don't want to spoil all my ideas, but given I doubt I'll do anything with it...
In my GoldEdge game idea, whenever you retrieve one of the Gold Edge weapons, you may run across a character who is like a cross between
Ghirahim and the
Joker from
Batman: Arkham Knight.
He suppose to raise red flags with his mannerisms but like most everyone in the game he encourages you to collect each of the Gold Edge Weapons. Every weapon retrieve he reappears to congratulate you while golden pieces of armour is added to him.
The big reveal turns out he is
Dark Guld, the spirit bound to the axe. He'll be a boss before or after Death=Adder as part of means of purifying the axe of evil or something like that.