Here's the situation:
Ideas come in two parts: seed and finalized.
Some people can create many seed ideas but can't finish them.
Some people can't create seed ideas, but can source seeds from others and create a final product.
Example: in Cujo, Tadder's dad is part of an advertising duo. He creates the seed idea, while his partner creates the actual advert based on the seed idea.
I keep wanting to call this Part 1 Ideist (eye-dee-ist) and Part 2 Ideist, but the internet says ideist is a synonym of idealist, which is someone who aims for perfection. Is there a word that means a person who creates ideas?