For many languages, a large set of ellaborate fst compilation is overkill. Also, it is not clear to users what the difference between the various fst's are. We thus need to fix two things:
1) compile only fst's that are needed (e.g. there's no need for both norm and desc if no Err/* tags are defined)
2) document the differences between the various fst's, and why the differences are there - there is some documentation, but it is deeply burried, and not easy to find if you don't know what to look for.
Each of these will receive their own bug reports.
Starting point for the documentation: