I've been working on digging on the foundation trenches and removing the flooring from what was the kitchen. Here are some progress photos of the kitchen floor: Here's what I'm up against as far as structural issues are concerned. This next photo shows a badly deteriorated joist and sill plate.
This next photo is of the sills and floor joists along the east wall, from below. Though not as severe as the photo above, you can see that the sills and joists are trending toward disintegration.
My plan is to remove floors in all affected areas of the house in order to gain sufficient access to raise the floor and replace the sill plate and floor joists. I plan to use treated lumber for the replacments. Generally, I avoid treated lumber where possible due to environmental and health concerns. Though I do plan to keep the crawspace much drier than it has likely been in its past, I feel like this is the most appropriate material choice. The crawlspace will still likely be a somewhat damp environment and the north wall of the house puts the sill plate basically at grade level. This, sill plate at grade, is not a good building practice, but what's a guy to do with a ~60+ year old structure? I may try to address the grading in the future...but for now, I'll work with what I have. I assume that the house was build before the advent of treated lumber, and I can certainly see some benefits to the use of treated lumber in this application!

I don't have any newer photos of my trench digging progress but I have slowly been working on it. I promise there will be detailed photos of the drainage system when they are worthwhile.