I think that most people in this thread have summarized the reasons why letting teams make their own motor controllers is not a practical idea, as there are so many things that can happen when hand assembling something to handle this amount of power. Even if 99% of the motor controllers were done properly the 1% of them that fail can cause fire, robots not responding in a controlled fashion, and a bunch of other issues.
Some people might not have realized this, but we have published the schematic for the SPARK at the back of our user guide. We believe that people should be able to learn from the product itself and not just the use of the product. Here is the direct link (PDF)
http://www.revrobotics.com/wp-conten...1200-UM-00.pdf
If any student wants to create their own "homebrew" version of the SPARK we encourage you to try, because reproducing is a great way of learning. For a low cost way to make your own PCB's, my friends own Dirtypcbs.com (and regardless of their name make good quality cheap boards)