Are you supposing that the party could settle on a non-Harris replacement for Biden before their convention??
Getting delegates to agree on someone other Harris in smoke-filled backrooms in Chicago is unwise and unlikely, but at least within the realm of possibility.
Getting them to agree before they’ve even met sounds like pure fiction. And that’s what would be necessary to meet the Aug 7 deadline. Kamala Harris will be on the Ohio ballot no matter what happens in Chicago.