And now...yet another addition! This was actually inspired by Curious, 
when it hit me that there should be a difference between someone who 
SOMETIMES lights fires and one who can NOT help lighting one...maybe you 
don't have all-around Weak Will, but you just can't help that ONE 
disadvantage...

Hard to Resist: -2 points/level
  This special "add-on" disadvantage can be bought for any
disadvantage that can be resisted by making a Will roll. Every level
of Hard to Resist, up to a maximum of five levels, subtracts one from
every Will roll you make to resist the disadvantage. It also lowers
the "any roll of 14 or more always fails" limit by the same amount. A
maximum total limit of -10 points worth of Hard to Resist (-20 for
supers) is suggested; after that, buy Weak Will.
  Example: John has Pyromania with three levels of Hard to Resist,
for a total value of -11 points. Any time he has a chance to set a
fire and tries to resist, he must roll against his Will-3, and any
roll of 11 or more automatically fails.

Since most people play Weak Will is -4 points/level (I have yet to find 
anyone who, when they stop and think about it, feels that -8 p/l makes 
ANY sort of sense), this is a pretty good point break, but the "Lowers 
the 14+ limit" is a very big deal, and helps balance this out.