I was curious as to whether anyone knew if they were going to also allow the user the ability to customize formation audibles...

This honestly seems like a given, because if you truly have the option of having any play in a formation and, consequently, the ability to remove any play from said formation, formation audibles such as "slants" or "hb dive" might not even exist in a custom playbook (not in my book, at least ). It would almost seem silly to not have custom formation audibles, because if they keep the defaults for the formations, theoretically that would allow you four extra plays in EVERY formation.

I've read in this thread, briefly, that EA is looking into this issue, but if/when anyone knows the answer to this, I would LOVE to see it! This will truly get the creative juices flowing and allow for some amazing offensive and even defensive schemes. Great thread and thanks for all the information!