The idea of the Imperial-II seems to be a pretty good solution IMO if they leave the ISD in its emasculated state. I think quite a few people want to play this game and at some stage arrive with a few Star Destroyers that give a serious "Oh crap" moment to everyone else playing. EaW nails this 'Star Wars' feel quite often IMO, but I think either ISDs should pack more of a punch, or ISD-IIs should be implemented.
@TearsofIsha, that design point is fine, and I'm 100% cool with that. It's a good point. Give the Mon Cals stronger shields, and maybe speed. That's their speciality, and works for good balance.
However, I reckon the ISD should be the most powerful ship in the game in terms of weapons and hull strength, it is the flagship craft of a hugely powerful regime and a damn powerful one at that. This beast has serious flaws, but it should tear a pretty big hole in most things. Also, being a dedicated warship I would imagine it would be pretty well armoured, more so than a civilian ship (converted or not, well designed or not)