There have been a few requests to allow custom playbooks so I'll bring it up for discussion.

PROs:

Truly customize your coach by using any formation you want.
Be able to set audibles.

CONs:

Playbooks filled with all the high pressure plays. 
Tendency to run same plays on defense (kind of happens already)
Money plays on offense (guaranteed to happen)

Thoughts?

Here's one situation where it would be benificial...

Say you currently have a team with a pocket passer for QB.  This off season you go out and draft/trade for a mobile QB with the intention of implementing the pistol formation/read option into your offense.  If it isn't already in your playbook...you're SOL.

Me personally, I'd love to see it specifically for the audibles.  Would I remove/add a few plays?  Sure.  But I'm more interested in the audible aspect of it.