Can regular bike forks be modified to allow front drivetrain setup?
To cold set a regular fork by 30+ mm would no doubt weaken it far too much to use. The better starting point would be something like a 135 mm fat bike fork, common sizes are also listed in the Sheldon brown table you linked. 

Notice however, that three of the four pictures you found feature extensive modifications to strengthen the fork or supporting frame to handle the pedalling forces. None of them will have off the shelf forks, they will all be custom made, along with the whole frame; they have totally different riding positions to a regular bicycle. 

If you are serious about getting a bike with front wheel drive, it’s worth doing properly which would mean sourcing something specially designed for the purpose.