Sounds like you're pretty well prepared already. Good job.

I concur with the Kubota diesels ... they just won't quit.

In theory, there's no reason why the PTO (power take-off) wouldn't run a small generator. (I assume it would be a pulley-and-belt system?)

But: the challenge IMO is maintaining a constant voltage. Integrated motor + generator units (gensets) have a governor that throttles up the engine when the electrical load increases. I suspect good ones would have some sort of electronic voltage regulation as well.

All of this protects the equipment it's powering. Most stuff today is engineered for nice, clean, stable grid power. It will suffer overheating and/or failure from undervoltage or overvoltage conditions, especially for an extended period.

If you were powering stuff that's expendable, I suppose you could run the RPMs up to the maximum, apply loads, and adjust RPM (and thus voltage) using a pro-quality multimeter (cheap ones don't always read true RMS).

My 0.02.