Maybe we should define "invention" in terms of "design decision". An invention should be something that requires no fewer than three hundred design decisions to create.
They're already unable to handle other subjective requirements like "non trivial" and still struggle with the slightly objective "prior art". I don't think adding new subjective definitions would help.
In my opinion the biggest problem with patents is that it's impossible to put the theory in practice no matter how great the theory is. On paper, patenting only non-trivial ideas sounds good. On practice that rule simply doesn't exist because it's impossible to define objectively.
