Mr Barclay, Quark, Rom, Harry Kim and Tom Paris - could bring some canon and comedy to the stories. Janeway, Garrak, Major Kira and some TNG cast - would be better suited to more serious stories and appearances (if they do follow The Orville, and include some more serious stories involving the light hearted characters) Other than those, I am not sure who else would suit the show. I think being able to be a little meta, and self-deprecating will make or break any cameos.
Why not Kirk, Uhura, Chekov, and Sulu? This could be the great opportunity to bring Kirk back. I can imagine that Quark would be a given. Same with Q. Maybe even Neelix.
They could recut existing voice tracks, with permission from the families He was up all night trying 100 hairstyles for promotability. In the end, he wakes up, and we see the E fly away (at least we, the audience, should get a nice view after so many years!)
I think that would be a bad idea, it would sound unnatural and really Odo and Nog have no reason to interact with this crew, especially since Odo is back in the Gamma Quadrant. This visiting DS9 and meeting Quark would be easy and would not have to involve Nog or Odo.
Where was it stated that Mirror Kirk was dead? I recall speculation that Mirror Kirk might be on ENT. I think Synth-Kirk would've gone over a lot better than Synth-Picard. From Memory Alpha: https://memory-alpha.fandom.com/wiki/Mirror_universe The mirror universe was intended to be featured in an ultimately undeveloped two-parter which was concocted in the hopes of enabling William Shatner to appear. It would have been revealed that a method of exiting the mirror universe was via the Tantalus field, as it didn't actually disintegrate but in fact relocated its victims – which had included "Tiberius", the mirror universe James T. Kirk from "Mirror, Mirror" (as played by Shatner) – to a penal colony in the prime universe. [3](X) "And so by that interesting, fun notion, you would have a world where all these Mirror Universe characters had been living," stated Manny Coto. Returning to the mirror universe was of paramount importance to Tiberius and thus, when Enterprise NX-01 arrived at the penal colony, he was excited by the prospect of it allowing him to journey back to that reality. Much to his chagrin, however, the mirror universe didn't exist yet. In this narrative, it would have been created by Tiberius himself, as an alternate timeline split off from the prime timeline following the events of the show. ("Before Her Time: Decommissioning Enterprise, Part Two: Memorable Voyages", ENT Season 4 Blu-ray special features)
Let's have Synth versions of all the other Captains show up! Including Lorca and Pike. In fact, let's just throw a Synth Michael Burnham in there, just to troll the haters.
In a really short scene that was just someone overhearing a scene from the past play out word for word, how would that work in this series with Nog and Odo?