Few of the things I will be working on to make this even more realistic include :
1>Customising eye shader (you can choose your own shader for every NPC you are spawning at runtime)
2>Hair color change and several hair variations, I will be providing with limited sets of hair meshes , but you can obviously export this into 3ds Max/ Maya and create your own hair mesh.
3>Clothings -> Clothings can have variations in color and texture , and currenly will be limited to jeans/trousers/shorts and shirts/t-shirts and jackets for men , but you can always increase the size of your cloth library by creating your own. Use marvellous designer for quicker implementaton.
4>Animation->May be you can change the walk style of your character from unreal engine itself , without modifying the animation in Motion builder? I will see if I can implement this functionality. Not impossible , all you need is few slider values in the blueprint , and the distance , bent , rotation between the legs/feet, hands, head rotation, body bent , will be determined based on those slider values.
5>Skin texture -> I am looking forward to implement realistic skin shader. you can control the material parameters to randomly create dynamic skin material instance for every NPC you want for each character, by tweaking few values in the blueprint. I am bad at writing shader logic , so this will be saved for the last. 