Obviously the carbine would've been nerfed, as is now tradition with a new Halo title.
Joking aside, I think we have to accept 343's vision, and either enjoy it, or not. At the very least I'm trying to understand it, piece together why certain decisions were made, and certain changes implemented, even if I can't embrace the version of Halo they've created. I do plan on writing a big piece on the game, and some of these decisions, but I'm continuing to play and think about the game as time goes on. I won't talk about campaign as much, because I think people like Ghaleon and Dax do a much better job than me at dissecting that side.
One thing I keep coming back to is that somewhere down the development cycle the team got excited about something, something that we now think of as a poor change, or one at odds with the traditional balance of Halo, but an idea that grew and spread within the team, and at that time felt genuinely exciting, fresh, and innovative. I believe that this excitement relieved a lot of the pressure from a team that were under great stress to create and evolve such a beloved franchise, and for that reason they clutched towards this idea and vision without properly stepping back and asking why?
I could be, and probably am, completely false, but right now that's the only explanation I can offer for how a team so devoted to a particular ideal and ethos can land so far from the goal.