As long as armor abilities keep gameplay balanced, I don't see anything wrong with it. I agree with you that they need a skill-based ranked system, particularly one where if you win, you go up, if you lose, you go down. A no scope medal would be pretty cool!
And as far as seperating social and ranked, I once thought this exact solution but 343 will probably have the ranked playlists with armor abilities as well. The one that would be the least likely to have them is the MLG playlist, which I'm sure 343 will keep around (since they're doing a good job paying attention to the MLG/competitive community).
As far as bloom and maps goes, I agree. I've said it many times that bloom causes to many shot inconsistencies. 343 should bring back those awesome maps from other Halo's. Some of my favorites include Midship, Lockout, Warlock, and Construct as well as the ones you mentioned.