Aeolia was in suspended animation. did *you* watch the show? And plus, it was more like 200 years old -- he was around in 2100 when he was making his contributions.
And yes, I know they killed Lockon, but they also "killed" Trowa in Gundam Wing (at the same point in time, if I recall right -- right before the end of the first season), which is somewhat where this series was started off of. They didn't show much more about him, other than that he floated off. They also "killed" everyone else. So who's to say his death is just the same? If Graham is coming back, I don't see why he can't. Tieria is more than likely back, but with some new "programming." Even if the voice changed, maybe they just flipped a switch to make him a girl. If he's a robot or whatever, it's not like him disconnecting his GN drive and floating in space is going to kill him. More likely, they'll just recover his body later and say, "Hmmm, ok, let's make him a girl. He looked like one anyway."
--Terin