Hello, I am not sure how many people here use Unity 3D, but I came across this rig for Mechanim on a website and tested it out, all I do is use this rig, export as fbx, bring it in to Unity and set T-Pose and use Autorig and all works really well. I am seeing no strange things as I do with the other rigs. I have applied many Mechanim animations to a few models and love the results.
see attached, rar of unity3d.json , extract, drop in MH folder data/rigs and it will show up in your MH choices.
Credit to who ever put this together.