It would be far simpler to setup my DVCS to track JP's remote copy of my ticket's branch...then simply pull from that remote...make my changes and request he pull from me when he's ready to review. Automates the whole process quite a bit and reduces the round trip yak shaving.
Any reason you can't do this with our git or bzr mirrors?
Or for that matter, you can include e.g. an github URL in the ticket instead of attaching the patch.