Flaws are too broad to all fall under a single power level. For instance, becoming blind and deaf is a much harsher flaw than gaining the Superstition derangement. Thus, flaws need to be broken up into Lesser, Medial, and Greater variants. Since flaws are so incredibly varied, rulings have to be made on a case-by-case basis, but these guidelines should at least help.
These rules are written with the assumption that characters do not gain XP when a flaw of theirs impedes play, contrary to the core book. If allowing XP from flaws, consider making it harder to gain XP from a commonly-invoked flaw than from a rarely-encountered flaw.
Lesser Flaws include things like a mild derangement, a trick knee that makes you extra vulnerable to a targeted attack, or Forgetfulness. They're things that only rarely come up in play, and can be bought off with relatively little XP or roleplay.
Medial Flaws are generally severe derangements like OCD, losing an eye or a limb, or most book-listed Flaws. They seriously affect the character, but don't remove the character's ability to use any skills. The amount of roleplay needed to reverse a Medial Flaw is substantial, but it can be done.
Greater Flaws fundamentally change the character who receives them, and include becoming paraplegic, losing hearing and speach, gaining extreme derangements, etc. These flaws almost always remove the use of one or more skills and are almost impossible to get rid of through XP and roleplay.