Exactly .... give room for new roles and characters to up and coming new actors.
William Shatner was a minor actor in the 60s until he became Captain Kirk ... same with George Takei, Nichel Nichols, Leonard Nimoy, DeForest Kelly .... their participation in Star Trek established their careers.
I love the new Trek because it keeps introducing us to new faces and new personalities that we've never seen before.
Cage has already done lots and he'll probably keep doing more because of his already established fame. He doesn't need to be on Trek .... maybe a short cameo but not a main character.
While not as big as your examples, I think Matt Frewer is similarly affiliated and his TNG episode turned out ok. I think it could be done, with the right script.
I agree the script matters and maybe it could be done without being sucky. Not that I don't love Cage but... I think Fewer is a bit better actor. Maybe not to quite the level of disappearing into the role like some do but still.
I think Michelle Yeoh was pretty well known by the time Discovery arrived and beyond initial recognition I kind of forgot all about who was behind the character. Likewise I forgot all about Whoopie Goldberg, it was just Guinan. (Maybe give Cage an iconic hat? Lol) David Ogden Stiers did well right? (I don't remember that episode very well).
I'm not sure if it would be as easy to blend Cage into a show.
First of all, I don't care how good of an actor you are (and I'm lukewarm on Cage), you shouldn't get to have anything more than a cameo on a show just because you love it.
Secondly-
In that 2023 Yahoo interview, Cage praised Chris Pine’s portrayal of Kirk as well, saying he thought the new J.J. Abrams-produced Star Trek movies were “outstanding.”
If you like the J.J. Trek movies, fine, but to call all three "outstanding" does not sell me on him being the big Trekkie he says he is.
Both of those seem like a bad idea likely to ruin the audience's immersion in the show. I think he could be a one episode guest star as, like, a Ferengi or something though