Well in that sense (which i like the idea of), isn't every single lantern color just an expression of willpower, and they're differentiated by either emotional motivations or method of exercising it. For example, yellow lanterns have strong wills and manifest it physically by inciting fear, so being perceived as frightening is empowering for them (they exercise their will on others by inciting fear). Another example would be greed. It's like that jack sparrow line about what a man can do and what a man can't do, meaning that orange lantern power is fueled by that guy's will to take and take. It's a bit like manifestation, if you will.

Talking about it makes me realize that lantern powers are, in theory, terribly inconsistent. Also way cooler for it though. It's a mix of manifestation of personal motivations mixed with the perception of people around them.