Personally i always modeled from scratch for JA, i only re-used the hands. I've always built around the skeleton or kyle's mesh, sometimes i modeled from scratch and fitted them around kyle afterwards.
I guess it's up to you, if you feel this will be quicker or easier then you should use it.
The reason the mesh is all tris is because it was imported from the .glm. You could still convert it to epoly but it wont be much help i guess, i havent worked with editable mesh in ages myself, kind of obsolete with the epoly tools.