No, it isn't.
Not the part about him dreaming about the LIs, but the part about him dreaming about the LIs in this specific environment.
Why would he not dream about them in this environment? The mind is a crazy and creative thing, especially in our dreams, so there's no reason why he couldn't dream of something like this.
I'm not saying I'm right about this, but I just, for whatever reason, have a hard time wrapping my head around the idea of these characters playing this game together. Yes, Jill and the MC played before; yes, Josy and Jill are somewhat friendly; yes, Josy and/or Maya could be convinced to join by the MC or Jill because of their connection to them; yes, they might all be in the library along with Magnar and Sally, but that's an awful lot of conveniently coincidental circumstances for this to work.
Plus, having them all play together, especially if the MC is dating all 3, feels like it would force too much drama on this whole situation when we were just getting to a nice cooling off stage where hopefully the MC and his various relationships would get a chance to breath, relax, and take things easy, but this would take so much of that away.
