It would be great to have a powerful modelling tool and a game engine at once.
A complete integration (like seen with the BGE) is not possible because of the GPL (which forbids such interaction with commercial software).
The only known workaround would be if Unity maintained custom Blender builds (which would only be available to their customers, much like how Vray and Octane integration works).
that sums it up thanks
Live reloading assets on save good enough?
http://answers.unity3d.com/questions/288243/how-do-i-refreshupdate-old-assets-in-unity.html