To me, it would be comparable to learning that “Lt. Leslie” from “Star Trek” had been an unacknowledged casualty in “The Wrath of Khan”...
Ironically, Transporter Chief Lt. Kyle --
-- was back in Star Trek II as the Communications Officer of the
Reliant, Commander Kyle:
Per Captain Tyrell, his crew was marooned on Ceti Alpha V by Khan and secondary sources hold that the entire crew was recovered -- including Kyle. So not a casualty,
per se, but he
did only have a few generic lines and then was removed from the action by the baddie for the rest of the film...
By the same token, I see no reason to bother including him in the films if all you're gonna do is have him say, like, 3-4 lines and then blow him up. It's the worst approach to fan service you could take, and I already take a pretty dim view of fan service from the outset. If you're gonna use him, use him for real and make his appearance meaningful to the story (not meaningful to the fans necessarily -- those two aren't the same thing). If you're not really gonna do much, just have it be literally any other Mon Cal you want, and you'll give the fans less to be pissed about when you vent him into the void.
Over in my pile of "important information the audience needed to know at least
some of, ideally in the form of relevant additions to the total running time" (aka my big rewrite of Star Wars into -- pay attention,
Psab keel -- a trilogy of trilogies...
of trilogies), Ackbar helped get things going for the New Republic after the Battle of Endor, led the New Republic Defense Fleet as a Fleet Admiral at the Battle of Jakku, and then, after the Galactic Empire surrendered, retired to Mon Cala. When the New Republic ignored Leia's warnings about the First Order (not yet known by name), she coaxed him out of retirement to join her Resistance. Closer to TFA, he was captured and interrogated by Phasma as to the "location of the Rebel base" -- *ahem* -- and was brilliantly defiant until he was told Kylo Ren was traveling there to continue the interrogation personally. Before that happened, though, the Resistance discovered where Ackbar was being held and freed him.
Then he helped coordinate the Battle of Starkiller Base along with Leia from D'Qar and all of that. I think his final words are a perfectly fitting send-off, from the character, the actor, and the voice actor. As the torpedoes homed on the
Raddus' bridge, he looked around and took those final seconds to say,
It's been an honor serving with you all.
So his presence
was relevant, and
did have a point and a purpose -- and that was all left off the big screen.
I have great memories of obsessively reading the EU as a teenager though when I revisited Shadows of the Empire about ten years ago I was shocked at how poorly written it was. I'm going to reread the Thrawn trilogy one last time for nostalgia sake and I hope I enjoy it like I did then. I read it at least 2 to 3 times back in the day and I hope it holds up.
Heck, I only marginally liked it even at the time. I never felt the characters "sounded" right. I appreciated the new characters introduced -- Mara and Winter and Thrawn and Pellaeon and Karrde -- more. I liked the gaslighting of the Noghri and the whole "Lady Vader" thing. I liked the concept of the Emperor's Hand. I am
not happy at how material from those books was employed in Rebels (mainly the
Chimaera and Captain Pellaeon being with Thrawn back before the OT, as well as the unprecedented chimaera relief paneling on the Star Destroyer's hull) and the new ancillary canon (I had hoped "Rogue Squadron" would be one part of the EU left in the bin, and it's Zahn's fault -- Brian Daley started that ball rolling, but it probably would never have been remembered beyond the ESB radio drama if not for HttE). I never understood the popularity of this trilogy. I liked having new Star Wars stuff, but liked what Dark Horse was coming out with far more than the first few years of novels in the Star Wars Renaissance.