Warriors of Light - Dice mechanic considerations

 Yep, my idea of a game now has a semi-official name: Warriors of Light. It'll do for now. Therefore, until I change it again all game-related stuff will be labelled with that or "WoL" so you can follow along at home if you like.
 So, right or wrong, I am starting this colossally-huge project by thinking about the dice mechanics. I know a few things I want and a few that I don't so here's how this went:

Dice scheme                               What I like                                     What I don't like
D-20                       It's simple, roll a d20, add your mods                Pass/fail, no greys unless
                              compare that to a target and your done              the GM adds it.

GURPS                  Still fairly simple                                                More complex than
                                                                                                          d-20, Still no grays

Dragon age            Stunts                                                                   Still pass/fail

FUDGE                 Pluses and minuses give some grey                    

Warhammer           Success & Fail AND Advantage &                     A bit more complex than
                              Disadvantage built into the dice                          I was hoping for with the dice pool


 Well, as it's the closest I found, I am gonna steal Warhammers' "Story Dice" because, with the dice pool and 4 states, you can Succeed but cause a Disadvantage as well as Fail but cause an Advantage. I like this. Also, in WFRP the PLAYER rolls all dice and helps shape the story by interpreting the results.
 In WFRP you can't have a critical success unless you have applied at least one skill rank to what you're trying to do. This makes sense but eliminates the "Critically Lucky" factor of rolling a natural 20.
 I may change my mind later but, for now, "story dice" it is.