Developer Sandbox
I know you’re already aware of this, but figured I’d write it down anyway. >_<
In such a sandbox, it would be great to simulate dates and charging cycles… Waiting 29 days to test out a feature is a little inconvenient. 
Ability to alter user, campaign data
Being able to alter a user’s data. For example, setting their avatar. Along the same lines, being able to alter the description, rewards, goals, etc.
Make posts, send messages on the creators behalf
Similar to the above, the ability to make posts (with links/images/attachments/polls/etc) would allow some really nice integration with other apps / sites. As an example, there could be an app that stores post templates that the creator has made, which they can easily change information in a couple fields and then send out the newly generated post instantly.
Improved Clients & API Keys Page
An improved Clients & API Keys dashboard would be great, especially if additional permissions like those I mentioned above are added. Perhaps some way to choose which permissions the client asks for, rather than only having the permissions added by email. Plus, it would let us see what permissions the client asks for. If I didn’t know that my Patronizer client had multi-creator access, there is nothing on the Clients & API Keys page to let me know that.