I think morale enriches combat and allows PCs options on resolving combat other than slaughtering their enemies mercilessly. When I finally introduce fatigue mechanics (the fatigue saving throw concept), I plan to make morale an off-shoot of them - morale checks will be a type of fatigue check. Turning undead will be a morale check (specifically, it will force undead creatures to make a major fatigue check, and will be one of the few ways of forcing them to make such checks).
I also think that yet another feature fighters should have is the ability to force morale checks in certain situations. This represents the awe-inspiring and disheartening skill with which they dispatch their opponents, or perhaps merely their savagery. Mindless monsters like golems and undead will have special rules about making fatigue checks that will make this less useful against them. Two proposed powers:
Ferocious Hewing: Whenever a fighter deals sufficient damage to kill an enemy, he can force one other opponent to make a morale check. Failure means they must cower or retreat for one minute (DM's choice).
Champion Slayer: Whenever a fighter of 5th level or greater deals sufficient damage to kill the enemy with the highest remaining hit dice, he can force all remaining opponents to make a morale check. Failure means they throw themselves on his mercy or flee screaming (DM's choice).