that's why they're putting Halo 4 on dedicated servers, to limit cheating, but, how they can stop derankers? they can't monitor every game and all people have to do is get 1 kill and go AFK or jump up and down and they will be fine, like in H3, they can't ban people who only get 1 kill, because then they can say they were just sucking in that particular game, keep doing it, and so on, IMO, the way to stop it is for them to check Game History constantly, and have a report system with that specfic gamertag so they can monitor them.
Also, in further reply to your MLG question, you are right, Apart from Instinct, none of the MLG pros liked bloom, and i agree, after having played ZB for a while, i really enjoy it more then bloom, but, apparently halo is been taken out of MLG because they won't make a profit compared to games like Starcraft or Counter Strike, and even CoD, compared to them games, Halo is tiny, and, that's a fact, them games (Starcraft / CS) are some of the biggest competitive games in the world (Because of E-Sports) Halo doesn't have that, so, according to sundance, Halo is going through a "Transition" year.
Ranking system shows more then exp though, Ranking system shows your skill in the game, Exp shows how long you've played, you can be an inheritor and still suck.
And, what's wrong with Jetpack / Sprint? They are probably the 2 most balanced AA's in the game. IMO, Sprint and Jetpack made halo better, fair enough, they can take the others out, but Sprint and Jetpack would add a new element to Halo 4, and, judging from the teaser we saw, they are not ruling using AA's out.
Im sorry, but DMR > BR with no bloom, the dmr feels so much more consistent and so much more accurate then the BR, but, they will probably use the BR because they are trying to make a "classic halo."