I had an idea recently for how you might be able to implement sprint while still addressing the concerns that no-sprint folks (such as myself) have about map design and the combat loop with its inclusion. Forgive me if someone else presented this idea or some variation earlier in the thread, but with nearly 850 pages to go through I don't exactly have the time to ensure I'm being original here.
The basis of the idea is that rather than have sprint as an instant activation by a player pressing a button, you have it as a passive activation from a player's forward movement. So let's say you have CE-3 base movement speed, with the ability to shoot, melee, throw grenades, all that good stuff. After ~7 seconds or so of forward movement on the player's part, they would begin to sprint at however much of an increase to movement speed, unable to shoot/throw grenades/melee without dropping out of sprint, which they would then have to build up the momentum again in order to sprint once more. This would allow a map like Midship or Warlock to exist without enlarging the map (and thus lengthening the sight-lines) by accounting for sprint, because odds are in a 4v4 Slayer match you're going to get into a fight before you've sprinted across the regular length of those maps, and will have to regain that speed again once you have. It also allows sprint to remain as a decent traversal tool for larger BTB maps in the event you are unable to acquire a vehicle, or campaign levels in general where balancing against other players is moot.
I went with 7 seconds here for the obvious reference, but also because I think it's a good number when considering the criticism that sprint makes escape too easy. Having to commit to the sprint for seven seconds would hypothetically force the escaping player to be more aware of their surroundings to keep cover so they are not killed while trying to run away. And if the following player is unable to kill the runner within those seven seconds, he likely would not have been able to if the game had no sprint in the first place. Not being a game designer myself, I could see this number either going up or down depending on actual playtesting, and almost certainly with the time to sprint in the campaign being lowered to again reinforce its use for traversal (and have the value be fully adjustable in custom games besides). I believe playtesting would also show whether it would be necessary to have the TTS countdown be reset when a player is shot, have it add additional time per shot/amount of damage taken while building momentum, or if the length of the TTS would be sufficient on its own. I might air on the side of only the time commitment as the deciding factor, but that could change depending on how the testing played out (though I personally think the TTS for multiplayer should be no less than five seconds at absolute best, and no less than three seconds for campaign). Odds are you would want a player getting shot to knock them out of sprint as well, but I admittedly haven't given that aspect much thought as yet.
I also wanted to talk specifically about how this sprint system would work with the Energy Sword, since the inclusion of sprint has made the sword a much more offensive tool than it was in the original three games. Since any attack forces the player out of sprint as is, the inclusion of the TTS would make it harder for a player with the sword to sprint around cutting down the enemy team, since they would have to once again build up to a sprint after every kill, thus making escape after a kill and running to the next one more difficult. This puts the sword back into a more defensive weapon, which I personally think is for the better. I also considered the possibility that switching weapons during a sprint would cause you to drop out of it as well, so that a player could not sprint around the map with a BR as a fakeout and then swap to the sword just before getting in lunge range and keep their speed. This would make sword sprinting a full commitment on the player's part, and thus making them a more obvious target for the enemy team when doing so. This possibility would also make it harder to sprint in with the shotgun, gravity hammer, and other such power weapons without being noticed by the opposing team. I'm not sure how weapon switching forcing the player out of sprint balances out with the regular weapons, however, so I believe this possibility would definitely need some testing, perhaps resulting in it being a power weapon exclusive factor, but I'm not sure.
And on a final note, removing the need for sprint to be tied to a button press has the added benefit of freeing up that button for other uses on the controller, whether that be some all new mechanic, or just putting crouch back onto left stick on the default controls (where I believe it should be) and help de-clutter the somewhat cramped controls that I felt Halo 5 suffered from at times.
There are likely other factors I have not accounted for in my reasoning, but that is part of why I am posting it here, to see what everyone else thinks and what they believe would improve the concept. So please, let me know what you think.