"Ion Cannon in the game?" WHY WHY WHY !!! leave Star wars out!
There is a disabling weapon but is does not have to, and should NOT, follow the Star wars convention of ION = disabling.
And you think starwars is the only science fiction that used that idea? The idea is actually very plausible in reality, as is much of the starwars universe (although not their space physics). I can't stand the people who have been exposed to one scifi universe and when they see a similar idea being used in another scifi universe they claim the new one is copying or something the one they were exposed to first. I don't think there is a single original scifi idea anymore because they are all used, largely do the the science part of science fiction.
Anyways, I think an interesting idea for a cruiser would be that it would have no weapons, but would function much like the ECM tank from C&C Generals, in that it would disable a ship for as long as it could cast it's ECM beam on it, there would of course have to be balancing issues to insure noone could make an entire fleet of them and disable the entire enemy fleet, but still, something to think about.