You know the Engineering Ability? I'm not talking about that.
What I'm talking about is the ability, once an enemy's shield is down, to board and capture the vessel.
Go to Engineering and take over the drives.
Beam onto the bridge and hold the command crew hostage.
Cause mayhem on the Crew Decks drink their brews in their crew lounge fridge, and steal a shuttlecraft.
Get killed while boarding and you reappear on your own ship, and the opportunity to capture that prize is lost.
Why would you want to do these things instead of just turning an NPC ship into a cloud of debris? Aside from the lulz, you could get Rewardz!
Marks appropriate to the faction which owns the ship.
Dilithium and EC for bringing the intact vessel home to display its broken hull... err, to allow the scientists to study the alien technology, yeah.
The opportunity to add that ship's card to your Admiralty fleet. (You still have to buy the card, the capture just unlocks it.)
Finally, for those NPC ships which are not available as a PC ship, the opportunity to fly one. I would only extend this to NPC ships which cannot be gotten any other way. There would be a purchase price, (fitting out fee,) to make the ship playable.
So why do this at all? Aside from the fun, that is? It gives Cryptic a reason to build ship interiors, and gives players a use for theirs. Boarding Party Training Exercises could take place either as PvP or as coop making use of the player's ship interiors. It could come out as part of an expansion and grow from there.
I think it would be fun. Plus, Boarding Party Accolades would be sweet.