Yes... like the layers of an onion this house... I've already replaced one footing and associated post in the basement, shoring up the rest of the beam with a 2x6 load bearing wall per engineering report. Also almost all of the 2x8 joists have been sistered since they were cracked, rotted, cut through, missing or rotting. The half story joists have to be sistered because.... one half of the house's joists aren't resting on the center load bearing wall.
At this point, I think it's easier to rip up the planks and replace the whole thing instead of piece meal replacement. It's going to be a real bitch getting that plywood up there by myself... maybe. I think lifting it up through the ceiling will be easiest.