I did something similar with a Midnight-ish Rokugan game I ran a few years ago. After getting backgrounds and such from everyone, I chose what seemed to be the virtue or trait they cared most about. They got a list of powers based on that trait. From memory... let's see here. The Crab samurai got the Soul of Duty, which gave him resistance and toughness buffs (Remove Fear, Bear's Endurance, and such). The Lion courtier/marshal got the Soul of Courage, which gave him group combat buffs. The naga ranger got the Soul of Nature, which gave him druid-y powers and a better animal companion. Things along those lines.
What I didn't tell the PCs at the time was that the Soul powers also provided them with the ability to survive death - at the cost of the powers themselves. The first time one of them died, I described a crackling lightning bolt connecting the spirit to the body, and a rush of power as they were pulled back to life - and a sense of draining, exhaustion. The powers came back over time (costing experience). I did this mostly because the setting didn't have any access to resurrection magic - outside this, if they died, they were pretty much out of the game.
I found it to be very successful - the group really enjoyed it, and explored where the powers came from and such.
