As I am not familiar with XMF, this is a shot in the dark but can XMF use Pitstop Actions Lists? If so, you could create an Action List to remove all content except the die lines.
pd
Here are the commands in the action list I have:
Select all
Select spot color Die Line
AND
NOT
Remove selection
It will remove everything except for any content colored as a spot color named "Die Line". You can of course change the spot color name to anything you like.
Hope this helps,
pd
Select all
Select spot color Dieshape
OR
Select spot color All
OR
NOT
Remove selection
Select all
Select spot color All
Select clipping objects
OR
Select spot color Dieshape
OR
NOT
Remove selection
Assuming you are using InDesign, put all content (except the die lines) onto a separate non-printing layer. Try exporting a PDF now.
pd