The other thing would be the Falcon attached to the back of the command tower.

Woh, missed that falcon on first glance.

I think this all boils down to peope wanting a fantastic Imperial Star Destroyer model with out building one.

Now, all this said, there is a canonical picture of B-Wings destroying an ISD at the Battle of Endor.

The only thing that is proof of, is that B-Wings were flying away from an exploding ISD at the battle of endor. We can't even say for sure that those B's attacked that ship, in fact the caption on the Wookieepedia page says "B-wings flee from an exploding Star Destroyer during the Battle of Endor." So that is not even close to being canon proof of B-Wings destroying a ISD.

But there is plenty of canon to prove that a flight or even squad of B-Wings lack the firepower to kill a ISD on their own.

Maybe an actual model isn't the way to handle Star Destroyers. They could be left entirely outside of the play area and be represented by just a (big) card and some upgrades

Flames of War does this for Battleships and in some cases arty, there is no model on the board, but you can still use it to drop a AoE strike.

To put it simply though regarding the ISD.

Having one on the table is pointless. You can not make one fit into the X-Wing game and still have it be anything close to what it should be.

The size, the power, the purpose of the ISD makes it unsuitable to be part of the X-Wing game, as anything more than a backdrop.

And what a mighty back drop it would be.

And what a mighty back drop it would be.

Yes it would.

And after a bit of thought, I remember that GamesWorkshop already produces set pieces that you use as terraine that cost $100 or more. So perhaps there is a market for such a thing.