I'm trying to construct a fictional reality out of the Socratic-era (ideally) theories of Forms, but every philosopher's attempt seems to have at least one fatal flaw (and most of them several big ones), from Aristotle, Parmenides, Plotinus, Plato, Zeno, etc. Have any philosophers (in your opinion) managed to make a fully/almost fully consistent worldview out of the concept of Forms? Ideally, someone who existed before 600AD, but if there is a really great one, I'm happy to accept one all the way up to the modern day.
To be clear, I'm not looking for a theory that maps reality well, considering it's a well-discredited area of thought, but one that has the fewest problems with contradicting itself so I can create a fictional reality out of it.