A couple of thoughts:
IMHO, its throws the "cosmic balance" off if you have Skyfathers (Earth-level Gods) busting galaxy's...
You have Elder Gods, Cosmic Cubes, then (seemingly) several levels of true cosmic level beings above Skyfather...if you have Skyfathers busting galaxies and Cube Beings warping entire resisting universes, then that makes the Abstracts, Celestials (who were described by a Cube Being as being "several orders of magnitude" greater than itself), and the other Universal forces unrealistically powerful...
I actually liked how the Odin Force was toned down when "King Thor" possessed it; being able to perform major Earth-level feats (like reconstructing Earth's Moon) seems fitting of an Earth-level God IMHO...
As concerns the AD...
It was always my impression that the Destroyer had a base level of power that it operated on when animated by an ordinary soul...
However, I also thought that the Destroyers power grew in direct proportion to the "soul strength" inside it at a given time; ie...with a strong soul inside it, it would be more powerful than at "ordinary soul" power levels. With several weak souls inside of it, it should also be at greater than "ordinary soul" power levels as well...
Now even though I dont have any proof to support this, I believe Thanos possess's a powerful soul (I believe "soul strength" is equal to a beings will power). Thus I really do believe that the Asgardian Destroyer animated by Thanos would be operating at a level much greater than "ordinary soul" power levels...
Maybe not enough to cause the armor to grow, but enough to make it significantly more powerful than it would be normally...
As a result, I also am of the opinion that Thanos has a very real chance to beat Zeus here. Assumming that Thanos has his body well hidden, how the heck is Zeus going to harm it?