I made some custom challenges and sent out invites to them. Just to give you an idea on credits:
I made one challenge to achieve 5 headshots: 313cr payout
I made another where you have to get 5 multiplayer wins: 2024cr payout
So, it looks like the credit payouts will actually be worth it and we should be getting quiet a bit of credits from regular challenges and our custom challenges.
Time to get busy tonight!