I would consider paying more than C2 if we have :
1. Solid "UNIVERSAL" Ads and IAP plugins in place. Right now monetizing our games is a nightmare, we have to run behind Plugin developers for every single issue.
2. Support for making Isometric perspective games including map editor, path finding. Elevation (slopes/upper floors)
3. Animation screen to tweak frames per second and see the result instantly , rather than having to run the game everytime
4. Native(C3) support for Dialog box system (Message box, Popup, Input box) where we can assign our own sprites(background and buttons) and call them in a single line of code. Currently we have stitch together number of small sprites to build various popup screens. Managing the Click event for each button and handling Visible/Invisible properties becomes a nightmare after a while!!
5. Inbuilt function that automatically tells me if users is on a Touch Device or PC with Keyboard and mouse. This will help us decide if we need to show users instructions for Touch or KB/Mouse (if on PC).
6. At runtime, allow us to DESTROY/Flush out assets from Layout that are no more needed so that some memory is cleared. I know C2 loads all the graphics into memory when a Layout is loaded. But often there are sprites that are no more needed after certain time. Eg: I show users set of instruction of a large Popup box that will appear only first few time. After that it doest have to appear anymore, in this case I should be able to tell C3 to remove these sprites from memory.
7. Native support to create and test Font Sprites
8. Universal Leadership and achievement board plugins for all major platform (Android, iOS and Windows)
Again, I love C2 so much.. I might end up buying C3 anyways