Firstly you are welcome to apply for this character! Secondly, after some discussion we have decided that Ren would need to stick to one body, and we do allow for "humanization" upon characters entering the game. The body you choose for him to have can be his All Mate body, his body in Rhyme, or should you choose the appropriate canon point, Sei's body; but it will need to be one, rather than switching between.

Hopefully, this answers your question!