It is very lovely to earn money from saved civilians,and mission performances.Still,more sources can be added to the game.I think about one-shot missions such as saving a CEO or such VIP from a Terror mission.For example,in every terror mission there could be a secondary goal,given by a phone call from a corporation,stating that one of their VIP's are stuck in the terror mission.Success should make players earn much cash,while failure gives great dissatisfaction to the Corporation,which can be translated in game as unhappiness to the government you did the terror mission on.
Any more ideas?You know,one never has enough money in XCOM similar games.