Get these bonus COs after you win the corresponding mission in Normal Campaign mode:
Adder (costs 1,000 points): Win Mission 26
Candle (costs 3,500 points): Win Mission 26
Chakka (costs 3,500 points): Win Mission 26
Flak (costs 1,000 points): Win Mission 26
Grimm (costs 1,000 points): Win Mission 20
Hawke (costs 1,000 points): Win Mission 26
Javier (costs 1,000 points): Win Mission 20
Juggler (costs 3,000 points): Win Mission 26
Kindle (costs 3,500 points): Win Mission 26
Koal (costs 3,500 points): Win Mission 26
Lash (costs 1,000 points): Win Mission 26
Sasha (costs 600 points): Win Mission 20
Zipo (costs 3,000 points): Win Mission 26
To get these bonuses, do the following:
Gallery (costs 2,000 points): Successfully complete Normal Campaign mode
Mistwalker: Successfully complete Hard Campaign mode
Oozium (costs 1,000 points): Win Mission 22
Soul Of Hachi: Successfully complete Hard Campaign mode
Soundroom: Successfully complete Normal Campaign mode and buy everything from Hachi