Possible to Replace Seat Belt Webbing in Explosive Pre-Tensioner System?

Seat belt works well in my 1999, but the webbing is frayed. New material is on hand from a donor system that lacks the explosive pre-tensioner found in this 1999. Is there a way to safely extract the worn webbing and spool up the new stuff?

Every thread I found resolved with sending the whole seat belt system off for rebuild or with full replacement with the full rig from a Toyota dealer. Maybe there's a reason for that, but how do the refurbisher folks replace webbing?

 

In case this is relevant for someone down the road:
.