We know this already. Once the design is ready, we need to try it in the game as soon as possible. What works in the designer's head might prove terrible after it's implemented. Mechanics need to be tested and balancing needs to be tested. The earlier issues are found, the easier it will be to go back to the drawing board and fix them.
Iterating, as we have discussed multiple times in this book, is the key to a successful game. Modern game engines and prototyping tools give us no excuse to be too lazy or too confident and just skip to the final implementation.
Unfortunately, we are not able to practically do this and the next steps, as it would require having access to Overwatch's source code...but this is what you'd ...
