Star Trek expected you to put Star Trek first. That's the basic gist of everything being said right now on the Delta Flyers podcast. Original hosts Garrett Wang and Robert Duncan McNeill started the podcast to talk about their former show, Star Trek: Voyager, but after completing the watch-along, they since switched things over to cover Deep Space Nine, and added Terry Farrell and Armin Shimerman to the lineup.
Farrell played Jadzia Dax in the series, and Shimerman played Quark. They're often cited as two of the most liked characters and actors from the show, so their additions made sense. While covering the first season episode "Dax", the crew talked about the missing Colm Meaney, who played Chief Miles O'Brien on DS9 (and formerly The Next Generation).
He was missing in the episode due to him filming a movie, and that sparked a conversation where (thanks to ScreenRant) the hosts talked about how the producers of the Trek series would shoot down requests for time off during filming to take on new projects.
Terry Farrell: "That was pretty cush. For [Colm Meaney] to be a regular on a TV series and fly and go do movies, and come back, that's awesome."
Garrett Wang: "I do feel he had that written into his contract beforehand, because any time that Robbie and I tried to get time off to go do anything else, we got kiboshed, every time. It was like, no, sorry, this is your main job. Whatever other thing that you're looking at, you can't do it. Sorry."
Robert Duncan McNeill: "It had to be in his contract."
Terry Farrell: "Yeah, it did. Because I couldn't get out to do something either. ... It's not fair. And I wasn't asking to go away for 6 weeks, I was asking for 5 days."
Meaney likely had agreed to do the flim before his contract with DS9 was signed, meaning it was grandfathered in. And while it may be upsetting, it's understandable why the producers and showrunners shot down other requests. There's only so much time you have to film, and you really can't justify missing a week of work when you know it'll be a few hundred thousand dollars extra after they return.
It's why they were fine with Farrell leaving in season seven. While some may see it as petty that they killed off her character, they had a story that was bigger than one actress and they weren't going to be handcuffed by someone who didn't want to work full-time.