What's the point of creating such toy 3D programs? Blender already has huge amount of free training material, any serious development effort would want to integrate with its UI, rather than strip it away.
I'm thinking of scientifc simulation tools, which would benefit from interactive 3D graphics. Coding that with a traditional game engine is a no-go for researchers.
For more detail see: https://www.blender.org/development/projects-to-look-forward...