I like the idea. I'm 100% comfortable with a female gender and set of pronouns, but I can think of several members off the top of my head who don't fit the existing categories. Moreover, there are multiple possibilities of what an "other" might want to be called. Haiz' "ze/hir" is one example, but I imagine some would prefer "they" to more novel terms.
As long as it doesn't remove any existing options, it sounds good to me, at least as an experiment.
That was more or less my thought: allow people to state exactly what it is they wanna be
called--and there's lots of pronoun sets out there!--without having to make any statement as to what they actually
identify as unless they want to. So Haiz would be one example, in terms of having a specific set of pronouns ze likes; while people who are actually cisgendered but don't want to disclose their gender on the internet (like me, in many communities) might decide they want us to call them by they/them/etc. Just a way of making things a little more welcoming, perhaps?
(And yeah, this most likely wouldn't take away the existing gender feature, just rename it and add some things.)