There is the Arena Expension Mod by Janus but the latest release is for 0.751.
http://forums.taleworlds.com/index.php/topic,6620.0.html
Yet, Kolba ported it to 1.011 to include it in his mod, Chronicles of Zendar.
http://forums.taleworlds.com/index.php/topic,39316.0.html