tl;dr:
I'm not worried Zoey is going to steal the other LIs' lewd scenes, I'm worried she's going to steal the focus that should be theirs in the wake of the crossroads. And no number of saves can help against that unless DPC is willing to dial down Zoey based on our actions. I'm not holding my breath.
ename144, I like your insightful posts, but I think you worry too much.
Is Zoey going to cause drama? It's BaDIK, yes.
Is Zoey going to be a new MG/LI, or more like a Quinn type significant SG? We don't know.
Is Zoey's introduction going to distract from relationship building with other characters? Probably to some extent, screen time for Zoey means somewhat less for others. How much so, we don't know.
Are our choices regarding the Zoey vs other relationships going to matter? Some of them, which ones we don't know. Maybe we'll be able to largely relegate Zoey to the sidelines, like you can with Quinn (important to the story, little impact on your other romantic relationships). Or maybe there will be big impacts on all our other relationships, DPC likes his soap opera drama. Either way, we don't know.
Is introducing a major character into the game midway a significant disruption to the story? DPC has been dropping new characters (or elevating their significance) throughout development, some more warmly embraced than others. The reintroduction of Zoey seems to be a major plot point that was planned from the start, so it can't be a disruption of the story DPC wants to tell. How well that works for players will vary on their tastes/expectations. We won't know until it actually plays out.
All that worrying must be exhausting. I prefer to just embrace the mystery.