Hello,
After digging further and inquiring about it on IRC, I was redirected here by ab who said that Thierry might have more information about this project.
I'm currently reverse engineering existing plugins and I am planning to use the SLAPI_PLUGIN_PRE_SEARCH_FN hook instead of slapi_compute_add_search_rewriter written in the doc to harmonize it with the SLAPI_PLUGIN_POST_SEARCH_FN needed to process the results.
I'll be happy for any help/feedback you could provide.
P.S. : plugin source will be available to the community once it has been completed or reached enough maturity to be used in its experimental state.
Regards,
Thelvaen.