I am an experienced DIY'er and have designed and installed supportive type flooring in older homes (mine included), which passed muster with our strict building inspector), so I'm thinking that I will end up correcting this. (I know, it should be a professional job, but frankly they can't afford anything close to that).
My plan is to run a sister pair of 2x12x20 beams from the front of the house under the house and just inside of the exterior piers. I will then excavate (combo power post digger and elbow grease) down about 36 inches at the ends and in the center. Into which I will place a cinder block at the bottom for a footing. I will use FHA post jacks in all three spots to bring them up to the new support truss, and will pour concrete around the jack bases up to ground level. Next I will begin "lifting" the house with the jacks, alternating between them to share the load, until i make up the drop, plus a tad for compaction of the footing. Once set, I won't abandon the existing cement piers, but will use metal step shims betweent the piers and end plates (using a hydraulic jack to get the end plate up a bit) to bolster the very end of the house.
Does this system sound like it will help? I'm sure the problem was partly due to no gutters on the house and surface water erosion on the middle piers. What pitfalls have I missed? Thanks for your help!