Why Oda doesn't simply hire someone to draw at his place if One Piece is so taxing?
Watch yourself here. Oda has repeatedly said his favourite part about making One piece is the actual drawing itself
Even in a recent interview, he revealed that he created the ENTIRE Skypiea Saga so that he could draw the Straw hats partying around the campfire in the Sky.
Entire arcs are created just so that Oda can draw an image he has in his mind. The concept of Monsters and Ryuma and Wano exist specifically because Oda wanted to draw a Samurai behead a dragon
If Oda ever stops drawing the manga itself, the manga will either end or become 1000 times worse because the actual drawing is Oda's favourite part.
This isn't a Togashi situation.