You know how in Halo 2 and 3, health automatically recharges, and you don't need health packs. Is this possible in CE, which I'm almost certain it is. Does it involve complex scripts?

It does involve complex scripts if you wish it to recharge slowly. If you just mean to have it recharge immediately when your shield recharges then that's no problem at all. I'd be happy to share my scripts either way, just say which method you prefer.

(global short number 0)

(script static "unit" player
(unit (list_get (players) number))
)

(script continuous healing
(unit_set_current_vitality (player) (+ (* (unit_get_health (player)) 75) 2) (* (unit_get_shield (player)) 75))
(if (< number 15) (set number (+ number 1)) (set number 0))
)

The number scales where for the default Halo 1 Mastercheif. It recovers 2 health per run of the script, it should be about 4 health recovered every second (out of 75)

So I can just paste this:
(global short number 0)

(script static "unit" player
(unit (list_get (players) number))
)

(script continuous healing
(unit_set_current_vitality (player) (+ (* (unit_get_health (player)) 75) 2) (* (unit_get_shield (player)) 75))
(if (< number 15) (set number (+ number 1)) (set number 0))
)

and have some nice h2 health?