Kongregate should bring back the Co-op mode. For now the only way to play Co-op is on Ninjakiwi's Website, and I do not want to restart my account and rebuild all my progress from Kongregates BTD5
I think that the daily challenges should offer a greater reward. They offer very little monkey money, for difficult challenges. I personally have not managed to beat many daily challenges because they poses a challenge far greater than most player's skill.