Down, obviously! Although you can just consider perfection as a flaw for them to overcome -- they need to learn to compromise their principles for the sake of the mission or whatever.

I don't really like character development by deliberately planting flaws you plan to buy off later, though. I prefer to play flaws that I intend to keep, and only have the character change if they're really really forced to... after all, that's what it takes for real people to change.

...and then, if possible, have them not change anyway. Nya ha ha ha.