Yes, you're exactly right. The defenders will get a little bit of E, and the attackers, instead of being Co-E, will still have a more pronounced advantage, and also not be bothered by Ack. The problem with defending in this situation isn't just getting some E built up; it's getting the attacker to dump his, and jump him when he does. Your idea would encourage no attacker to get slow, or give up his advantage in altitude energy. They'll come down, 2, 3, 4 or 5 at once, fire off a short burst, and the hurri/zeke/il2 that got wheels up has no place to go, and no advantage against any of the attackers.
If anything, this utopian scheme of yours would only make the situation worse.
To clarify my concerns regarding this proposed change to gameplay:
The easiest way to land a sortie of more than 5 kills, for the vast majority of players, is to vulch. The second easiest is pure cherrypicking in a many-vs-few engagement. Both yield the same results, and provide the same padding effect insofar as scoring/ranking is concerned. When you eliminate the easiest method, the second easiest method becomes the path of least resistance. That's my concern; that instead of these clowns being consumed with vulching, they'll be overwhelming any fights that have developed whereever the vulchers have been overrun.