Your numbers don’t quite add up, in your example it’s 50 draw calls vs 250 draw calls 
So you have saved 200 draw calls, but you have added a lot of complexity to your pipeline. All character and armor meshes now have to use a common base material. You have to be very specific about UV layout, and features like morph targets or material parameters are harder to use.
There are certainly cases where mesh merging is helpful or even necessary, but we feel for a lot of games, the better tradeoff is to use multiple skeletal components. We do want to have some good examples or tutorials on that, and we are discussing here quite what we want to do. Once we have that covered, we probably will try and cover merging, but for the reasons mentioned above, it is a little lower priority.
Have you tried using the existing FSkeletalMeshMerge code?