TextCat currently seems more promising than the baseline ES Plugin we've been using. It's in very old Perl and should be converted to PHP.
Stas has already started working on converting TextCat to PHP for use in Cirrus Search (available on GitHub: https://github.com/smalyshev/textcat), and he and Erik have been brainstorming on ways of making it more efficient, too. It needs some testing (e.g., Unicode compatibility) and comparison to the Perl version (i.e., same results on building modela and running on test queries).
Rough estimate: < 1 week