would a thief of light be one to tend to reject their role and believe they are more "powerful" than they are, wanting to be a lord or have an aspect like hope?

I mean, honestly, not really? Because Classes and Aspects are arguably neutral and never more powerful than others. Lord could be an exception given, Master Class, but even then it’d depend on who the Player is and how they’re using their powers. So no, because ‘Hope’ isn’t directly stronger than ‘Light’.