For consideration.
When Epic was considering release of UE4.0 it was not completed as to full feature completion but worked well enough to release in it’s current form and then continue development. I noticed this from the start as the over all quality was not up to par with the UDK release required as a completed application.
This was a real first as the community was invited to take part in the process by making use of what was available and in the process would improve features with each “preview” build. This route seems to be working as appose of holding back workable features and the control rig makes a good example as being a TA there are missing features that goes beyond the ability of simply being able to animate in app. If you look at Motionbuilders control rig or Mayas FBIK system it would solve and even remove the need for retargeting in UE as a control rig would allow the use of Epic animation on any rig with out consideration of naming convention.
Long way of saying where we are now is not where things or going as feature inclusion is not even completed which can be frustrating how ever using external apps like Blender, MB,Maya or 3ds Max would be considered the best solution.
The way I would put it is doing animation in UE is like using a spreadsheet to write a book. It would work but is not ideal