I’d like the Campaign levels and the Multiplayer maps to be made so that players can utilize cover without actually implementing a cover mechanic. There are far too few locations in Halo where cover is actually practical. These covers could be walls where only your upper body is exposed, and walls which you can crouch behind.
I also feel this would work great in Campaign, especially if the enemy AI is tweaked to always try to fire at your chest so that chest-high walls can be effective. I think this would add a greater sense of immersion since running and gunning would realistically be the worst idea against the Covenant or Prometheans.