So let's imagine a DS9 sequel series or TV movie is green lit and you're the producer. Does Jadzia come back? If so how? Or does Terry Farrell come back in some other way? Or is she not in it at all?
Aside from flashbacks or time travel, there’s always having Ezri do some sort of meditation/dream sequence/other Trill something-or-other wherein she encounters previous hosts, one being Jadzia. That’s happened a few times on DS9.
Well, they call it a blending of the minds in that TNG episode (“The Host”), but once Riker takes on the symbiote, he doesn’t retain much of himself at all. He’s all Odan (the Trill character). Riker is only able to host the symbiote briefly before becoming very ill. Once the new host arrives, they take on Odan’s personality completely. ¯\_(ツ)_/¯
The Trill were obviously in a prototype stage for that episode, as they appeared without spots, and with forehead ridges instead.
This is probably why Trill have to undergo years of training before joining, to keep their personalities more merged in.
It could also be that Dax prefers to be more passive in its relationship with its host compared to Odan. This makes sense because if the point of Joining is to gain new experiences, overpowering the host won't let the symbiote learn.
Ezri did not do just fine. She struggled with it constantly, especially at first. No, the training was necessary. It was the exclusivity that was manufactured due to the extreme scarcity of the symbiotes. As it turned out, almost any Trill could join, but that would cause a massive rise in demand, so the Symbiosis Commission claimed only very few were compatible in order to keep demand suppressed and the symbiotes safe.
I thought the big reveal was that almost all trill could be joined successfully, but since there weren't enough symbionts to go around they pretend that it's only a select few that can?
I mean, she slept with Worf, which is the one thing she's not supposed to do.
And like I said, there may be a difference in personalities between symbionts in how dominant they are. Plus Dax had lived through 8 pairings and knew Ezri wasn't trained. It could regulate.
I always thought we really missed out on a chance for there to be a more intense overwriting of Ezra with Jadzia, or one of the other hosts. She seemed so meek! Give me a St. Alia situation, where the current host can't stand against the memories of previous ones, and make it more compelling than taboos and stuff!