The most complicated of all the character classes are going to be Togabito, due to their constant state of being on the run from hell or being imprisoned within hell, and Zanpakutō Spirits since they will require another character in order to fully function. I find that for Zanpakutō Spirits, it helps to create a soul reaper character to go along with them or collaborate with another player who has a soul reaper without a named Zanpakutō. Personally I would love to see either one of these however.