The WOTC ones were actually pretty close to IA's when you take the poses into consideration.

To be fair, Armada's not to scale, they could realistically put an SSD in it if they so desired, the same way video games that are to scale have since forever: the Executor is so superlatively, idiotically big that you just have to make it huge and it looks right. Besides, look at the Corellian Corvettes next to the VSDs. It can't look more out of proportion than that. The SSD would only have to be two or three times the size of an ISD to work.

X-Wing and IA, however, like their scale. A few concessions to playability were made with the CR90 and GR75 but as a general rule X-Wing's to scale and IA hasn't broken scale yet (the IA AT-STs are apparently right and the WotC ones are wrong).

I used to argue this myself before I actually saw the models. Personally I don't think anything less than five times the length of the ISD would look remotely acceptable (and obviously still a fraction of the correct size) and that would be waaaaay too big to play wouldn't it?

I want it to automatically have an in game effect that is impactful but not broken.

And that is the real problem, it's also the problem with the ISD in X-Wing and SSD in Armada. It's not the size that's the biggest problem, it's the amount of firepower.

How do you properly represent something that has 10 times the firepower of a standard unit? The ISD has 10 times the firepower of a CR-90, the SSD has 10 times the firepower of a ISD.

The AT-AT may not have 10 times the firepower of a AT-ST, but it's an order of magnitude above most things in IA. Snowspeeders couldn't really damage them not unless shooting at a weak point, so what is Jan or Gaarkhan going to do?

They can't fight it in the conventional sense, so the only thing it could really be would be an objective type object. Not an actual unit that you move and shoot with. Plus, given the design of the thing there's no way it could hit the heroes on the map. They're already far too close for it to target them given even a large IA map... An AT-AT would actually need to worry about facing because those things can't turn around as quickly as even a AT-ST could, and would have to have a 15 square blindside in front of it where it can't lower it's guns far enough to hit.

So what you really have is a 3d model of mission objective objects... How much money is anyone going to really pay for something like that?