In the game of baseball there are very few reasons to actually swing on a 3-0 count.
In my career, I was given the green light only 5-6 times. Even then I only swung 1 of those times. I am 1 for 1 lifetime against MLB pitchers. I played against John Ely of the Dodgers back in high school and got a hit.
Any way on, make the pitcher beat you.
I actually would stand straight up and put my bat on my shoulder and not move. The pitcher always messed up when I did that.