Making up limits

[Sitting Loki]

Are there any guidelines on devising limits? I've read the examples from the datafiles, but was thinking along slightly different lines with this one:

Hesitant: if a d10 or d12 is assigned as an Effect Dice when using this powerset, replace it with a d8

Obviously this is a great candidate for XP use after a few sessions, but I like the idea of a hero unwilling to push themselves beyond just pulling their punches.

But back to the original question - what mechanics are available for manipulation through limits? If you think of a limit like "Cursed Fate" where a hero cannot gain more than 2PP during a single action, as long as you're willing to abide by the consequences, is it legit?