Yeah I'm not keen on us controlling our own opponents because we are essentially always fighting ourselves. My idea is the same as Fox's where we play each others opponents. However I want to stress that I would prefer us to do this RP for real storyline reasons, to make a really cool arc rather than treat it as the Arena and based solely around the fights. The fights will be pivotal and climactic but I want lots of twists and turns etc to make the story interesting to play out :) 

Speaking of, who has ideas for the reasons we are invading. Currently I'm thinking that it would be based around something a long time ago when an extremely powerful Shinigami was imprisoned similarly to Aizen. And whilst the Gotei won't know it (we can plot hax like Aizen) our true motive is to free that person, but we feign that we are trying to make the kings key or something that would act as a red herring to the Gotei.