@anonymous_user_e40f608c (fixed the attachment, thanks)
So my method to get my character here imported and reexported was to know some things about it. For example I knew it was originally -Z Forward and Y Up, I knew (by trial and error) that I had to scale it by 300x so this is now my default preset for importing C4D meshes/rigs.
The very first thing I do is make sure my import is facing the right way (-Y Forward) and is scaled roughly correct (make a quick Cube), then delete the cube, select everything in the scene and Apply Rotation and Scale. Now verify the size of the mesh and that the animations still work.
At this point you have a 1:1 scale correctly rotated mesh/armature etc.
For the Epic guy I had to have +Y Forward, Z Up, Scale 100 plus a couple of other tick boxes
Once again select all and Apply Rotation Scale, then start modifying.