Santhosh pointed out that size was very important[1] when creating WOFF files for use on Wikimedia sites. When I asked for help creating a subset of FreeSerif on the freefonts-bugs[2], Steve White said that was "one thing on the big To Do list".[3]
In an amazing display of the power of open source, Bob Hallissy from SIL produced ttfsubset[4]. Perhaps the i18n team would find this of a use when they need to produce WOFF fonts.
[1] http://lists.wikimedia.org/pipermail/wikitech-l/2013-February/066531.html [2] https://lists.gnu.org/archive/html/freefont-bugs/2013-02/msg00002.html [3] https://lists.gnu.org/archive/html/freefont-bugs/2013-02/msg00004.html [4] https://lists.gnu.org/archive/html/freefont-bugs/2013-02/msg00005.html