This is frustrating to me. Thread pool has been a requested feature for quite a long time, and I'm sad to see it's not being contributed to the community edition. Wasn't it supposed to be a part of MySQL 6.0 and now MariaDB?
http://kb.askmonty.org/en/pool-of-threads
Also, Pluggable authentication is in MariaDB 5.2 and later but I don't think that it ships with any plugins.