We have a working system!  Currently, working CSYNC-for-VOSS-4UC, operating autonomously.  Current functionality:
1.  able to create new cdets in BZ
2.  able to add any attachments for newly-created BZ's
3.  able to sync status-updates
4.  able to add comments to CDETS-side upon status-update
5.  able to sync: status, severity, hcsXXX-blocking fields
6.  automatically takes care of cdet-dupe-linking (i.e. when BZ-user marks one cdet as dupe of another cdet via BZ-interface, script will manage this on CDETS-side)
7.  able to resolve a cdet on CDETS-side without going to H-state  (currently this requires hardcode of target/included version, using "10.0(1)"

Performance note:  at around 200 cdets among 4000 BZ-bugs, it takes on average 15 minutes to run a full sync.