That's a good place to start, but it's hard to get the new cover to fit tightly. There would be a bit of trial and error involved. For a traditional Major League baseball, the cover is damp when it is applied. It stretches considerably and then shrinks down as it dries forming neatly to the core. The problems with using the original cover as a pattern is that it doesn't lie flat or true.
My advice is to soak the original cover, Press it flat and let it dry. Then, scan it into your computer. Then, take the scanned image and reduce it by 2%. This would give you a slightly smaller pattern with the stitch holes in the right places. From there, you can expand or reduce the pattern to suit your needs.
I hope this helps,
Paul