It'd be great to have separate files for config - one for the connector, that could be stored somewhere on Jenkins, and a second one included in git, changing on a per-project basis. This would increase the flexibility (some projects require different rules than others) while maintaining safe storage of Gerrit credentials.
One possible workaround I can think of right now is to wrap the executable in a simple bash script, and use that as post-build step in Jenkins. However, it still requires Gerrit host/port to be set in the project config - in case any of these change (rare but happens), all existing projects will need to be updated as well.