This can't go all the way to the convention, because they made the convention so late. They actually have to make the formal nomination before the convention, in time to meet Ohio's deadline.
The only path forward is for Harris to take over the nomination. This is far easier if Biden resigns totally. He can say he's doing it for medical reasons, even if all he has is a chronic case of notgonnawinatall, complicated by inflammation of the opeds.