The salvage/capture aspect of HW2 sucked royally compared to the original homeworld. Capturing over the unit cap is the absolute only way to go, and this was purposely taken out of HW2. Plus the fact that you can only have a handful of marine frigates at a time, whereas you could have ~50 salvage 'vettes at any given time before (and they were collectively tougher, since once one attached the vessel was in effect trapped). Add to that the fact that capture vessles now occupy a frigate slot, instead of the worthless corvette slot, and you've got a system that really sucks. The developers are quoted as wanting to make capturing a more integral part of the game, but it just ended up being one obnoxious thing to look for and find you didn't have.