Hi Everyone,
We are happy to announce that we have released a new, fast, robust and powerful editing and prototyping Utility “MXD Edit” to the asset store which allows you from editing or fixing existing models to prototyping levels in a very simple and efficient way, it is not intended for modeling as it doesn’t support UV mapping but will help you prototype levels and test physics before building your game assets.
Check out the manual here
here is video demonstrating it
it is only $20 on the asset store and it is extremely fast and works with even huge meshes with full support to undo\redo and for play mode, actually it can handle the limits of Unity when it comes to the mesh size so >50k is no problem
here is the link to the Asset Store