Here's an analogy for all you creative producers: When hiring a director it's like hiring the skipper for your boat. You own the boat and you know where you'd like to go. However, you're turning over control to your skipper. Make sure you're in total synch with this person and you trust them with your baby.
What if he is the writer also?
If he is arranging the financing then he or she owns the boat - but remember, you're handing the wheel (and your charts) to your Skipper...who is now the captain and in control.
With your columbus analogy, I see the financier as Isabella of Spain. She trusts the navigator to know where to go, and how to get there, not just hold the wheel. The skipper is often more like a cinematographer. (Sometimes, the cinematographer owns the camera too, but I like your analogy as a starting point.)