rig allows you to create new animations for the mannequin character, and, from that, also use UE4 retargetting to use other characters.
You can also change the mesh of the character, and your new character will be compatible with mannequin animations becouse the skeleton will be the same.
The video its on blender 2.76, it WONT work on other version, the fbx exporter changed in version, allowing for to be made.
The animation pipeline its still pretty shaky, due to how blender handles the NLA and Actions for animations, and how they get imported. You can assume that each blender Action strip will be imported into its own animation file, plus another track of whatever plays when you press the play button in blender.
It works by having actually 2 rigs, one its the fbx imported one, wich is the one we export back, and the one the mesh its attached to. That rig its completely unusable, so i created a new rig, wich is the Control rig, used to actually do the animations. The deform/FBX rig its constrained to the control one, so by editing the animating with the control one, the other gets the animations too. Dont worry, the exporter bakes the animation automatically.
The rig its very simple for now, just an IK for legs, and no IK for hands. You can edit the control rig all you want, feel free to add better IK/FK controls and other cool stuff to it, remember to share it back with the community. Anyway, i will add more controls to it so its better for animation, but now its usable.
Get it HERE
Reply to message with all the doubts and problems you have so i can fix it.