Sounds like you're on the right path. 

You should be able to just export the animation sequences tho, using James' rig. Shouldn't need to re-import James into Unreal each time. 

There is a series of unreal tutorials on youtube done by epic. They show you how to import animation sequences, along with a slew of other things. 

I don't think anyone has done a set of tutorials specific to Poser and Unreal combined so far tho.