I was able to make a shooter last year with only one motor and it shot the larger baseball wiffle balls. So it is possible to shoot the balls with a wheel powered shooter as well. One of the pictures should have a link to a video(may not work). The shooter was effective from about a foot range on a 12.5" high goal, but could easily be made to shoot farther.
Another shooter I made (sorry no pics) shot raquetballs like the ones from half pipe hustle. Using only 2 motor and a 1:25 gear ratio, I was able to shoot them about 10 feet.
Just by judging from my own experience, it would be possible to make an effective shooter for the balls, and maybe even one that could shoot across the whole field.
-Chuck