*Ahem*, I have been on Single Player recently, and I saw a good example of why they should be soooo weak.
Prison ship XT-19 was nearly destroyed by a group of Liberty Rogues.. the Liner would try to make the passengers happy; passengers don't really think that Battleship Weapons are a must for a holiday, they would much prefer random rubish that needs POWER to run, not some giant gun thing.. otherwise Battleship holidays would be SO much more popular. This also applies to a shield, they wouldn't waste the power that they could use to power all kinds of random entertainment devices , to power a big shield. "Yes, the holiday might be a tad boring, but you'll be as safe as if you were in the Battleship Missouri".
Anyway, you can't really argue with Kane that the civilians get worse weapons. Personally I've never been to America, but I'm guessing pretty much nobody has a nuclear missile in their backgarden, or a Tank ( unless its old).
Whatever, I'm not really convinced if you are ever going to drop this or not. Because if you havn't guessed it only your that want these changes pretty much.