Boo. I thought that being able to capture structures with Boarding Party was awesome. I just wish it worked more often (i.e. AI timing: send a troop when the target is likely to be capped and not destroyed), and that it had a faster cooldown (maybe fewer marines, more parties). But anyway: boo. Structure-capping is fun.
Just because it was 'fun' doesn't mean it helps gameplay. That said, I didn't know I could (would) do it. I can't remember what structure is was, a small one. But in a large battle I noticed one of my 'troops' wasn't moving. Didn't recognize the icon right away and zoomed in to find it was a structure (I think it was a mine (diggy not xplodey), since for a second I thought it was capped by a colony ship in some strange ability I was unaware of...then I saw the "boarded".)
But my armada was on a heavy system push to get to the AI nova-cannons...so I'm not sure what happened with it... Not sure if my colony Cap took the planet or we left it razed. So I have no idea if the structures work for you, work for you despite zone control, how detonation works or anything. So I have no idea if this was OP or a waste of the Cap's boarding ability.
THAT said, I like the idea of it and I think I would prefer it was in the game if-it-works. But I suppose torp-ships are supposed to be the bunker busters, capping may be considered too easy.