You'd need a carbide drill bit to make a new hole in it.
Not at all
There not that hard to drill to be honest as its mainly the teeth that are the hardest part I have cut down several blades before
What you need is a vise and a either a hacksaw or angle grinder to cut the blade to length.
Then you need to mark where you want the holes to be take an old screwdriver pozi works best sharpen it with a grinder to a sharp point now use this and a hammer / mallet to punch where your wanting your holes to go, works best if the blade is supported on a scrap piece of wood.
you should be able to get the holes through the blade.
Then clamp the blade down very securely as you dont want it spinning as you drill it Im currently using a £3 set of drill bit that I got from a supermarket.
Start drilling the holes with a drill bit the same size as the holes youve punched cleans up any burrs.
Work your way up the drill bits about a mm in size at a time until you reach the size your needing and it will drill it fine just dont try to drill it to fast slower speed is best
cheers Russ