I've been trying to set up my synonym analyzer. It works with synonym phrases.
Eg. shortness of breath, difficulty breathing => breathlessness
However, this will not cover phrases like "difficult to breathe". Also, there are other phrases where we have plurals and other cases which make the synonym file pretty big.
I like the ignore_case option with the synonym filters. I wonder if there is another option (already implemented or in the works) which allows me to canonicalize the synonyms not just on case but on word-root as well (stemming).