* Point light shadows
* Armature\ object animation editing in the editor
* Event Triggers (Timers, Area triggers) that trigger specific animations, sounds, spawning of entities etc.
* Compilation of game into .exe
* Built-in predefined OpenGL filters, with configurable parameters (such as HDR,  SSAO, motionblur) for non-programmers.
* Content Browsing inside the editor, with material\entity previews shown in the thumbnail or preinterview box for example.

So to elaborate on the previous point, the content is imported into the current project, or buffered(Whatever it's called, im no programmer ) and all assets used in the current level\game are shown in a built in browser.

* Custom Keyboard shortcuts
* When selecting a field to change(such as shadowblur), highlight the whole field so that It's easily and quickly edited, like Blender.

That's all I can think of for now Ambitious I know, but why not consider some of these in the long term.