Figured it out! I feel crazy stupid right about now but apparently you can translate the entire armature in object mode and create keys…
Just turn on Auto Keys, select (only) the armature in Object Mode, select the frame you’d like modify and move the armature. I’m sure there’s an actual way to do this without Auto Keys but this is what I’ve got at the moment.
UE4 treats the Armature’s origin exactly like a Root bone! Hope this helps someone out there.
