Conceptor

The Conceptor will be a new feature of the game. By paying $75 Monkey Money, you can create a tower, an agent, or a bloon. You can give it any effects, upgrades, or powers that you want. Then, the game will add prices (for a tower or agent), or a suitable round appearance (for a bloon) so that it won't be OP. This would be a great way to add in conceptions that didn't make it in.