Scratched a hole in my head.
I love a good problem... What if this happened in the field. I don't have fobs for mine, but hey, its a puzzle to solve.
Connecting to the starter is a good idea... You'll have to put the DS on jack stands and pull the wheel to get to it...
Its a no go on removing the grill unless you don't mind destroying it. Two of the screws come in through the top. Once the grill is 'out of the way,' you can drill a 1/4" hole through the plastic cover on the release mechanism on the DS of it 1" from the edge. This should put you just to the PS of a plate in there. Use a screwdriver through it to push it to the DS and it will release. No, I didn't try this. I did come in from the top and push said plate over and sprung the mousetrap that releases the hood. It should work.
I traced the cable release for the hood latch from the dash through over the top of the fender, under the battery tray, through the gap behind the DS headlight and over to the release. I used a screw driver to 'close' the hood latch. In theory if you could get ahold of the cable release and weren't worried about hurting stuff... You could do it up through the DS behind the headlight from underneath. You'll need a lead weight on some nylon cord and a stick 3' long. Loop the line over the hood release cable and pull like hell and it might go. Thats what the stick is for. You're not likely to get your hand up there. Of course there are a bunch of wires there for the headlight and its hard as hell to see from underneath. It all depends on your level of desperation.
Has anyone ever tried a slim jim on the doors of an 80? I've never had to try it. How protected are the locking mechanisms? I'll have to check that out someday when I upgrade my speakers.
Then there is the final option. A big rock. Which window on a FZJ80 is the least expensive? I'm guessing the front one, but its the hardest to get through and the messiest. The ones in the doors are the easiest to change out.
So... since you're not stuck in the middle of nowhere, submit to any inquiry that the dealer requires to get a real key. Assume that your ignition has been rekeyed. Congratulations you now have a GM. One key for the door... one for the ignition... Don't turn it upside down. That would be a Chrysler.
Grench