And there's the line to cross if you want to re-imagine the campaign. Much of Halo is the way it is because of launch deadlines, not planned development. Reused levels, un-usable Wraiths, and so on. Touch one, and it opens a can of worms.
Me, I'd still prefer that. I was hoping for a rejuvenation of the campaign in a way that did alter the core, the missions, the encounters, and so on to take advantage of modern tech and the benefit of hindsight. That's not the kind of remake it is, though, it's one that stays faithful to the original game.
Having accepted that fact, I'm impressed with how much they were able to cobble into the game while still retaining the core. The new visuals, new music, beefed up sound effects, terminals, skulls, online co-op...it's a pretty meaty package. Would I have preferred a bigger overhaul? Yup. But there's no telling how many people that would have alienated. I have no idea. I think it's one kind of remake done about as well as you can do it, and I've come to appreciate the approach for what it is rather than what it is not.