It is my personal belief that the armor abilities that were contrived for halo reach are also what ultimate but an end to most of the fan base of halo. I'm willing to bet that most of the people that did enjoy never played halo 2 or 3 very competitively. I used to be semi-pro at halo 2 and there was nothing I enjoyed more than the competitive nature that the game brought to the gaming world. I think everyone would be lying to themselves if they didn't think that halo 2 is what started the huge gaming competitions that exist today. The game brought with it a challenge and competitiveness that has somewhere been lost along the years. Yes, halo 3 had it to some extent, but the game itself was a slower pace in my opinion.
Without going off into all the reasons I think the game series gradually declined, I would like to state my opinion on the possibility of armor abilities. I think that they are, overall, a bad idea. The problem is that you can't make a map that functions with and without armor abilities. Every map in halo 2 and 3 was designed so that every player had the chance to make every jump, and every skillful maneuver that they could in order to gracefully move around the map. With the introduction of sprint however, this gracefulness was lost. Suddenly you can only make certain jumps at certain points in the game. An opponent my rapidly run up on you from behind and easily overwhelm you before you can react.
Back in halo 2 I played on 8-10 sensitivity. When I played against other players, I could take 1 BR shot, turn around, and be hit for hit with them on shot 2. Now they are still 1 shot ahead of me, but if I outplay them I still have a good chance of winning that fight. Almost all of this skill level is lost with the introduction of sprint. By the time I notice them on radar, they are so close that if I'm in a confined space I may already be getting hit in the face by melee. This is just a simple example of why I don't like the ability (Don't even get me started on the sword/shotgun).
TL;DR Anyways, I don't know if I successfully explained why I think it's a problem but I really hope that sprint isn't included in the game. It takes away from the skill level, and in my opinion, the fun.