I really do think that 3DGS needs to get "Realtime Game Editor" done ASAP BUT it needs to be up to speed of the Unity3D Editor.

I would have done it like Unity did - employ a C# programmer to code the editor that wraps the core engine API plus all the other stuff like shaders into the editor.

But it does not matter really if 3DGS's "Realtime Game Editor" is pure C++ as long its as the same features as Unity3D Editor.