Either way, it would be awesome. Hell, extend the idea. Simply have it "turn on" whatever it hits for one full second. If it hits a weapon, that weapon will just fire at whatever angle it's firing at, regardless of whether anything moves, or if it needs to conserve ammo. It could be wasting Vulcan ammo, or if you're lucky (or skilled) a reaper rack. An engine hit causes it to go full throttle, as previously mentioned.
I dunno... I really don't like it when your hand is forced like that. I'm not even a fan of the EM emitter and its ability to quickly circle your ship and disable every weapon. It's just really frustrating to be on the receiving end of stuff like that... to just be targeted with a weapon you can't defend against without a 360 degree shield.
Ships are going to get into your blind spots, around your shields, and you're going to have to take some hits, so I'd prefer it if you were capable of taking said a couple of hits without being too punished for it. If one ship with something like that manages to hit your engines, what, now one of your ships ends up flying off, completely isolating them from the group? Not really fun.
On a completely separate note, I'd like to state again how much I'd like some kind of communications jammer. Right now you are never surprised by your enemy. You can see their fleet layout from the navigation screen, you are notified what ships are being added to the battlefield and, most of the time, a view of almost the entire battlefield is pretty much always available to you. I just feel like some degree of uncertainty, or possibility of uncertainty, needs to be added to the game to make it a little more suspenseful.