Gravemind put all his ideas about what would be the ultimate Halo game. I thought I'd take a look at some of those elements and see which I liked, which I didn't, and why:
My preferred compromise would be a Resistance-style "sectional bar" health system, with the player using health packs to fully restore their health; the player's health would have limited regenerative capacity, and could sustain damage that won't come back on its own. The health bar would be divided into three to five sections, depending on which number works better for gameplay or for each particular character. The health bar would be a solid bar with no visible lines to demarcate the sections. Instead, it would change color as it diminishes depending on which section the player's current health level occupies, similar to Halo 1's health bar but without the less accurate individual squares that composed that one -- the colors would be blue, yellow, & red if there are three sections, blue, green, yellow, & red if there are four, and blue, green, yellow, orange, & red if there are five. Each subsequent section could be made to regenerate slower than the preceding one. For example, the blue section might regenerate at one-quarter the rate of the shields, while the yellow section might regenerate only one-eighth as quickly and the red section might not regenerate at all.
This really would be an Ultimate Halo, at least in terms of difficulty, unless the damage model were altered. In this case, players are punished doubly for allowing their health to drop precipitously. Not only are they close to death, with further damage threatening to kill them, but they are forced to wait in safety for health to regenerate longer than if they had taken less damage-- and at that time it would be less important.
Of course, if there are health packs available this difference in regenerative rate is moot, since they restore health fully.
I think the above scheme is unnecessarily complicated and not particularly transparent. Unless the indicator takes up a significant portion of screen real estate the difference in regenerative rate may not be immediately apparent.
Frankly I think the design decision required is bold: to either have regenerating health or health packs but not both. H2/H3 compromised by having your shield, as your primary line of defense, regenerate, while retaining a "hidden" amount of health. (Also not particularly transparent.)