Update on this idea:
Winter is coming quick and I'm getting a tad desperate for a Winter Project, so I went ahead and offered to buy the tractor from him.
The deal was that I'd come get it, put it in my shop and do a thorough evaluation of whether or not it was even worth pursuing and then set a price accordingly.
Charged the battery, cleaned the terminals, wired around all the various control modules and interlocks, hot-wired the fuel pump and jumped the solenoid and got it to start and run. It gagged and puked a bit but cleared up after a minute and ran nice and clean.
He agreed to the price I mentioned and planned to be here Saturday to sign a Bill of Sale and a resale agreement.
Spent a couple of hours dubbing around on the Innerwebz last night and found a PDF shop manual, printed out the appropriate pages.
Started troubleshooting this morning and about half an hour into it found a bad fuse. LOOKED good, but tested high resistance and was dropping battery voltage low enough that the Power Control Module wouldn't read it.
Replaced the fuse and cleaned a few connectors and it starts and runs just as it should.
So, I'll change all the fluids and filters and for a couple of hundred dollars he's back in business.
Dang. Now I got to find another project...