It likely wouldn't be a matter of difficulty (outside of disabling custom draft class player story lines a la NCAA draft class import and expanding the player editing interface to allow for editing of player scheme / development / predictability / etc. settings), it's a matter of EA Austin's priorities for CFM.
Assuming no CFM draft class editing - which we really don't know either way yet for sure - it would be apparent that EA Austin didn't feel that draft class editing was a priority over any other features they added this year.