Expecting the worse, we pulled up the 2-inch strip flooring to reveal the original porch decking.
The 3-inch tongue and groove deck boards were in great condition although 20% of them had been removed entirely when the area was close in and turned into a bathroom in the 20s.
Sloping at about 1-inch for every 8-feet, I think we will pull it up and sister the floor joists to sit level. Shae also wants to have a plywood subfloor installed underneath which would add even more stability, although I hardly feel that precaution is necessary it really doesn't hurt and the added cost of material is minimal for such a small room.
I also want to put some insulation in before putting the floor back down, but hesitate with all the added moisture present under there due to bad grading and a high water table. Insulation could hold moisture and rot the joists, at the moment that moisture evaporates and does minimal damage.