Well Laka has both sets of genitalia so they're intersex. I know hanako used Spivak for Magical Diary so E, em, eir, eirs, but that also required a class explaining why it was used (intersex, none binary sex species at the school). The few transgender friends I have tend to hate the word it because it sounds so impersonal and cold.
I guess it depends on how you want Lakadema to speak. If Laka uses a lot of 'This One' or a weirdly formal language then you could make up your own pronoun for the species. Or since Laka's the shy archetype you could always include a dialog where Josh/Lisa asks them what their preference is on a binary level and depending on their response tag future dialogs with the 'correct' pronoun depending on player choice. So if someone sees laka as male then the pronouns change to him and so on, but I don't know how hard that would be to code and keep track of.
'This One is unfit to be in your presence..'.
'So what do we use, you know, for Lakadema?"
"What do you mean?'
'You know, to call, her, er, him, er them?'
'If it pleases you Joshua, this One accepts either terminology.'
Which could go either interesting in addressing her species slavery or get squicky...yeah I don't know.