Say I wanted to create (and sell) an original design of the D&D 5e Player's Handbook, Dungeon Master's Guide, and some original cartography of Forgotten Realms locations. This would mostly be a reprint but original form and artwork. I understand that OGL doesn't cover this because the published books are under standard copyright law; Source and Source - Section 18-g

If this is correct on this, based on this, I need to submit a request to them and get permission before producing anything.

Does this sound right? Am I missing something that makes this ok via OGL? Has anyone ever done this that knows the process which should be followed?