Are there plans for any imperial big ships? Not exactly star destroyers as I feel they are simply too large. Even though I would love to see a Executor. But I'm sure there are others they could pick from the lore

We dont know yet, although some people expect them to be revealed at gencon in a week or two.

I agree with you, star destroyers would be way too big and expensive, as it has 60 Turbolasers, 60 Ion Cannons, and would have like 150 hitpoints.

Are there plans for any imperial big ships? Not exactly star destroyers as I feel they are simply too large. Even though I would love to see a Executor. But I'm sure there are others they could pick from the lore

The forum search function can be hard to find (narrow text box at the very top of the page), and it's not always helpful, but you can use Google to search a specific site, like so:

"site:community.fantasyflightgames.com imperial huge ships"

Doing so will take you to this page, where you can access literally hundreds of pages of speculation and argument about which Imperial ships we're likely to see for Epic play.

I can't wait for the Black Sun Hutt Star Destroyer that will use 4 large ship bases.

And so imp big ship 1479 begins!

Did I mention that the Black Sun Star Destroyer will be 1/2 off at Barnes and Noble?