Rather than figuring out how to adapt a specific game system to Mistborn, I thinkwe are perhaps better off taking a good hard look at the real requirements of mistborn from an RPG system perspective:
1- Must be easily adaptable to the background... not too tied to its own races and world
2- Its magic system (or whatever it uses rather than one_ must be flexible enough to handle allomany and feruchemy
3- It must allow for a level of nature vs. nurture. What I mean by this is that some people will have allomancy, some will always have more potential than others, and some will simply not have the ability at all. It needs to have a way to handle that some characters are just anturally inclined to excell, rather than just saving up xp.
4- Combat, magical and physical needs to handle extremes such as iron pushing and pulling, as well as pewter arms (near super-heroic capabilities)
5- I must accomplish 4 while still being gritty, and dangerous.
6- It "should" be able to accomodate rules lawyers or rules light preferences. (this is just in my opinion)
for 2, I think that a game system with a "pool", similar to how many systems use mana is a good idea, as it accurately reflects the chemical pools of allomancy. If such pools can be "burned faster" for more effect, then it might give us a couple of key components of both allomancy and feruchemy.
As for the combat extremes, few games have really done this well... Most heroic games tend to weaken the "normals" too much... D20 did this fairly badly... although I never played Feng Shui, my understanding is that the best way for a heroic feel is to have alot of "mooks". Doesn't this really sell normal's short? I have heard that GURPS supers got a bit clunky after a certain point as well. Perhaps the new Marvel system? But I think it is way too low on lethality as well. Not sure if anyone as thoughts on game systems that do "mortal" heroes well.
Of course item 6 can all come down to play style... but I would hate the system to be one that is so far one way or the other (liek Harn master, or Amber) that it is really limiting.
Just brainstorming here
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