I can understand why your nerfing them and think its a great idea, people might actually buy engines if they use something other then Efficient ones.
as far as I can tell these weapons are no better then the IV counterparts and the Efficient Impulse engines are getting nerfed as we speak. Can we see these weapons reflect the names they were given as your changing the rewards, why not change them all at once.
Until you get the aegis or Borg engines, the efficient engine is the best one available. the problem is not with the Efficient Impulse Engine it's with the rest of the engines offering nothing of value.
I've never used the weapons you list so i have no comment on those.