I don't think it will eventually work out. This worked in a classless environment, but it won't work well for fairly restrictive classes. It is very unlikely that Larian will allow you to change the companion class selected on the first level, which means that even respecialisation will be very limited.
Another thing is that Larian certainly realizes that something like this would be quite unpopular (like in DoS2), so if they decided to completely change most of the dialogue in the game based on player feedback, it is unlikely that they would not do so either. Especially since it is much less problematic to change.
If they were to throw all the current dialogue out of the window, expect to count another few years up to development xD. I don't think people want that, either. We will see what they do with the game in the end. It is a fine balance they have to walk, in either catering too much to players wishes and compromising their own artistic vision for the story.
Overall I think giving agency to playerbase feedback certainly is a good thing, but doing it too much either adjusting to feedback or not listening to feedback, makes the gameplay portion meh (which I saw in a fair number of survival games lol) or just alienating the playerbase too much. in short, I'm fine with things getting locked down after act one, even if it goes against the OG series formula. I am just giving them a a chance to make the game they want, while still listening too feedback and adjusting it where they reasonably can. I don't think totally rewriting the companions, at this stage of development, would be beneficial to us as players. Unless you guys want to wait until 2025 to finally play this game xD. If I gauge the steam forum is kinda on the verge of: where is MAH GAME REEEE!!!!! YOU SCAMMARZ and: I KNEW LARIAN WOULD FAIL AT BG3 xP.
I just really hope they manage to give us a bit more build versatility than OG baldursgate did in some ways. Having all classes and races would go a long ways to at least give us more options. I personally dont see replayvalue on the companionside, more on the level of branching of the story. I mean... BG one enhanced has a lot of companions, but some I rarely ever use. I mean Xsar and montaron I always ditch in Nashkel lol. So giving BG3 let's say 20 companions to choose from might look good on paper. But I personally doubt that will make me come back to the game beyond a certain point. Because in pretty much any RPG, the companions effect on the whole story arc (outside of the protaganist) is abysmally small.