Here's another bloke who signed up to just to post on this.
I think a good way to sugar the pill on this is to make it a player's choice what they give up, and have that sacrifice cause something in the world. It should also be a fairly short game, so that players can reroll and try out different combinations. I'd say, no more than six hours or so.
Here's my vision: A sorcerer has summoned six demons, and they've each taken over one of six cities/nations/races, by claiming their stone of power. Your job is defeat the sorcerer, but if you attack him directly, the demons all come to defend him. You have to decide which order you want to confront the demons in, and when you do that, you have to choose a power to give up. The citizens of the city/nation/race the stone of power belongs to would be empowered with your ability. There wouldn't be a hard block on attacking the sorcerer at any time, so you could just decide to deal with less than six demons, or maybe even none of them.
You'd start the game with nine powers. Three melee, three magic, and three special abilities. Melee would be divided into fast and weak, medium, and strong but slow, Magic would be Fire(high damage, low range), water(medium) and lightning(low damage, long range), special abilities would be speed, invisibility and flight.
Which ability you empowered each group with would change something in the world, like if you gave a warlike group invisibility, you'd hear about and see ambushes where they would just appear out of the night, if you gave a pacifist group a melee ability, their culture might be split as some decide to use that power. It'd be interesting to let you level your skills to make them stronger/more versatile by using them, and then weight the effects of your gift based on how much you'd levelled the ability you gave up.
The focus of the game would be replaying to see how different methods of victory play out. For example, if you use a pacifist route, and sneak into a demon's lair using flight and invisibility, lock him out of the stone of power by empowering it with your weak super speed ability, then just leave, you might force that group to take heavy losses to remove that demon and all his loyal, non-mind controlled followers themselves, rather than killing him and all his dudes yourself. Basically, who you give what would be an important factor. It would be like doing quests for the New Reno families in Fallout 2 or supporting a certain group in Fallout New Vegas, except actually going and killing the sorcerer and ending the game would have very little effect, it would all be based on their relative power levels.