As many options as possible for custom games.
Its a fact, people dont always like the 'official' rules in games. So why limit the custom options to random crates and initial funds? What i'd like to see is as many options as possible in the custom games lobby. Things ranging from 'Super Weapons: ON-OFF' , 'Pop Cap: ON-OFF-NUMBER =...' 'Disable Unit Type =...' to the average amount of ore in mines or/and Tiberium growth rate.
Will allow people to turn off and change things they dont like about the game and also tweak rules to offer different gameplay experiences.
Honestly, none. Seriously.