I've just read the Capes Lite rules (and will almost certainly be buying the full rules soon) and had an idea that this could be adapted really well to George R.R. Martin's world.  The focus on character conflict just fits perfectly.

The noble houses could take the "powers" role, incurring debt.  For instance, Stark could have things like "Winter is Coming", "Blood of the First Men", etc.
The "skills" roles would be those typically filled by commoners and dispossessed nobles.  Some examples would be Maester, Black Brother, Septon, and typical medieval roles like Soldier, Bandit, etc.
The "personae" doesn't need to be changed much, just adapted to medieval/fantasy archetypes.

Not having the full rules yet, I'm not sure how drives even work, so I haven't addressed that.  This seemed like a cool idea and a great fit, so I wanted to just throw it out there.

-Reed

The only advice I can give is to discuss things with the other players as much as possible before you begin play. It's certainly possible to have serious games of Capes, but it takes an effort from everyone involved. Other than that, I don't have anything to offer.

I really like the idea of the noble houses filling in for the power click-and-locks. It seems to fit in very well with the books. I'm a big fan of both Capes and A Song of Ice and Fire, so I'll be looking forward to hearing about your experiences, however it turns out.