Greg responds...

Yeah, I pretty much loved Shakespeare from my earliest exposures. I still have a crush on Olivia Hussey.
Macbeth was the first Shakespearean character we included, and he just seemed too perfect NOT to include. We needed an immortal and dangerous Scotish King with maximum name recognition. Who else was there? His inclusion led to all the rest. But frankly, it was inevitable given my interests. Besides, as I mentioned above, to me these stories really exist out there, waiting to be plucked down. IT HAD TO BE MACBETH, etc. Cuz that's the way it happened.