Well…for starters:

 The terrain editor can be expanded upon with more tools to provide better definition and sculpting of the terrains. Optional auto-terrain river and stream slope detection. 16bit grayscale import and export capability.

The material editor can certainly use some revamping to make it user friendly, intuitive and easier to compose complex and procedural textures. The ability to selectively “paint” your textures on… Perhaps add shader capability and 3rd party compatibility.

The tree lab can use some sprucing up too. It should allow for better tree manipulation perhaps allow for user spline control where the tree trunk can be given to follow the curvature of a manipulative spline curve for curvier trees. It should allow for object instancing and perhaps a feature to rival Vue’s Ecosystem (EcoBryce) with allowance to selectively paint your “EcoBryce” selections in desired locations.

The Sky lab can allow for atmospheric control and better ambient 3D cloud manipulation.

All import and export modules be brought up to date with easier predefined 3rd party import and export capability.

Faster render engine with options for either Vray or Mental Ray render ability.

Allow for object vector, edge and polygon selection and manipulation (push, pull, bend, twist etc.).

Almost forgot...user SDK. For user modular programing (plugins) and exchange capability.

Just to add a few.