Export and Re Import a rig made with Rigify

I have 2 character models, both rigged in 2 different blender saves. I just now realized I should have probably rigged both in the same file for this. Anyway, is there any way to export one rig with the character and re import it into the other file? Every time I try, this happens:

So thanks in advance!

I am using Blender 2.73 (should I switch to 2.77 for this?) and exporting as FBX.

I am trying to make a fighting scene if that helps.