I can definitely see Valhalla being in the canyon somewhere.
But you are right. I am not excited about the Blood Gulch remake. It was awesome in Halo CE, but that's Halo CE and not Reach. It was tailored for Halo CE, and it worked amazingly with its simpler gameplay. I know a lot of people are fans of Coagulation in Halo 2, but I thought it was awful compared to playing on Blood Gulch. My main reasons for that was most likely due to the different physics and rules that Halo CE had: i.e. the grenade physics, invincible vehicles, etc. For whatever reason that made the map much more fun for me.
Anyways, my main point is that a map can play much more differently in a different game. Yes these are all Halo games, but I don't need to tell you that they are in fact different games with, although slightly, different rules and gameplay factors. That's why I think it makes the most sense for Bungie to stop making all these remakes of previous maps, and to just focus on making new maps that will work in their current game. And we all know that it is almost impossible for them to make everyone happy with their remakes. People always find something to bitch about.