Hi Mark,
In answer to your question: yes you can tie a messenger to the halyard to lower the jib.
As the CDI is repeatedly used the halyard cuts a groove in the plastic where it passes over the top (there is no sheave) resulting in difficulty raising and lowering the jib.
CDI sells a replacement which either has a stainless plate over which the halyard passes or a sheave.  I'm not sure which. When I enquired 2 years ago for parts to replace the "top piece", the halyard (it is proprietary) and  ball bearings for the furler drum, the price was about $250.

Best Regards
Jeff Smith
www.http://JeffSmithPhoto.Net Radiant, 2009/201
Atlantic Highlands, NJ