What other editors have advanced geometry editing tools like you are describing?
And, if it would be “painless” to add, why don’t you try doing it yourself? The full C++ code for the editor is available. If it is painless, you set it up and let us know how easy it was.
We’re already being provided with the best game engine ever. If you want a full 3D software suite to go with it for free, pick up Blender.