I think you might need to specify what you are asking for here. The opponents are already supposed to be random (that portion just isn't programmed in yet). I presume what you are asking for is the option to 'add new players' using a 'random' selection button, which is slightly different than just having random opponents.
In order to clarify:
Do you want random opponents using the suggested # of players (already planned)
or
Do you want to make players in the custom menu with the 'random' option
..Don't answer 'both' >.>