I’ve been doing some tinkering with the aura I was working on for one of my games(to be honest, I was already trying to get a slightly similar effect…), this is an example of the “mesh aura” technique which I slapped together by taking the original mesh, and inverting the normals, and smoothing the mesh details a little. Then I set a material to the “mesh aura” based off of the one demonstrated in this video here which lets it “wave” slightly.
http://www.theblackdawnwars.com/wp-content/uploads/2015/07/AuraMesh.jpg
It gives the outline effect fairly well, but there’s portions of the mesh that overlap with the underlying mesh, so it’s not exactly perfect or ideal, but it should give you a general idea of how to get started at least.