In Ghost Experience, health regeneration can be set to "partial", which causes HP to regenerate up to the segment of the health bar that was partially drained from a taken hit.
I feel like a great addition to this feature would be if the size of the chunks could be customized to further specify the strength of the healing factor.
For example, 6x16.67% health segments instead of 3x3.34%.

This option would serve as an intermediate between partial and disabled HP regen on a higher enemy difficulty setting, where you would almost always regen only a tiny bit of health after being shot.
It would also make bullets more potentially deadly on lower enemy difficulty grades, where 1-2 shots taken would permanently shave off a small chunk of your health, whereas with current partial regeneration you're often able to kill or run away from an enemy (group) before they are able to deal an entire third of your HP bar's worth of damage to the player.