I would rather see a separate new game for "Ships of the Line", there are still several ships they could use for cinematic play that don't really breach the size limitation of X-Wing. I prefer to play on 3x4 foot or larger boards so using the larger ships currently planned won't affect my table play much.

If they did release an ISD for this game, sadly I would buy it, then it would sit on a shelf decoratively and I'd add the cards and tokens to my available stuff, and the ship itself would never hit the tabletop for a game ever, I just couldn't bend reality that much, and my imagination is crazier than most (see attached pic, I did the world a favor). I also agree the imbalance issues would be insanely bad, I can't imagine the points I need just to field a fleet of Rebels large enough to take one on if it remained true to the real thing (let alone the cost to buy all those Rebel ships).

There are things about adding larger ships I do like, and I am also loving the fan effort to put larger ships into play, a lot of impressive kitbashes and self builds out there, but super ships... new game please...