If you need three-phase power for big machines, that's gonna be a big ol' expensive generator. But you'd only need this to work while people are there and running the machines, so you might not need as much fuel on hand if it's not going 24/7.
I'm guessing you might need two generators: a smaller setup (powered by gasoline or propane) for things like lights, computers, fart fans, beer coolers, router, etc. and a separate heavy-duty generator, maybe diesel, for the times you need to power the machinery. And do you need this to fire up automatically even if no one is there, or can it wait until someone shows up?
And then there's the question of monitoring; since you don't live there, some sort of camera/monitor system on a battery backup with a wireless (cellular) data connection would help keep you apprised.
To clarify, is this more of a personal shop, or a commercial shop, like a repair, fabrication, or manufacturing facility? Is it just you, or are there employees who will need to be able to work if the power goes out?