I think if you take the water dish out for a bit it should be okay?
My concern with using it would be if the vitamin e leeched into his water supply. If I was to rub some on, I would probably take the water dish out for a few hours, then use a damp washcloth to remove excess oil from my snake before putting the water dish back.
Concerns for safety aside now....
Is this something for an injury or shedding aid?
I think the only time I considered using it is when I had a badly scarred rescue with difficulty shedding over the scar tissue. In most normal cases where there's no healing injury, vitamin E is completely unnecessary. Most shedding issues can be corrected with better monitoring and extra humidity in a hide when coming to the end of the shed cycle. If your snake is routinely having some skin issue, that sounds more like some sort of metabolizing issue the vitamin E oil won't help or improper husbandry.
I honestly don't know how well a ball python can tolerate that high of a dose, so it isn't something to take lightly on an otherwise healthy snake.