I think even using it a little would open the floodgates, just as in Star Wars. Fortunately Star Trek has had a well established history of using other actors to play their characters.I could see the argument for using deep fakes or AI tech to insert the faces of TOS cast members if it’s just gonna be a single scene or small handful of scenes. The whole idea of “prime Kirk IS Shatner” etc…
I don’t necessarily agree with it. But I get the argument. It’s like using de-aged/AI Hamill as Luke in “The Mandolorian” and “Book of Boba Fett” or the Leia/Tarkin stuff in “Rogue One”
Now, if it’s a much larger role…say inserting Nimoy for Spock or Hunter for Pike. Then no, that would be too much.