I was going to say Stephen's thoughts were interesting ideas for the reboot, but I thought it wouldn't come off right. Since you bring it up, I think a reboot would help a lot of issues. I don't think so as much since about a week ago, though, because I realized that if they rebooted it they'd be doing what they're doing now, they just wouldn't have previous canon to try to reconcile with or justify or wash away or whatever, it would be more or less irrelevant, they might even go farther without restrictions-- and that's a sobering thought because I don't like most of the directions they've taken Halo in, independently of their canon agreement. I want quality stuff more than I want canon adherence, that's why Reach's canon breaks never bothered me that much-- the game was fun and the story wasn't too special but it didn't seem out-and-out bad.
As for trying to hold to canon or not trying and justifying it and how to justify it, I think it mostly comes from a single flaw, a bug in the human system if you will; to cite G. Carlin, 1981, "[T]heir stuff is shit, and your shit is stuff".