Still relatively straightforward biologically. Just two yes or no check boxes rather that one this or that checkbox. Maybe add a "can change?" checkbox for each of them. That's what, 16 options."Species" is rather like "sex" - it is presented in a very simple way to laymen, but the actuality is not straightforward.
(Unless you're talking about fungal mating strains, but it's arguable whether or not those fit the definition of sexes since the gametes have the same overall morphology)
In a way, a biological scientific standpoint is simpler because it cuts away all the extra baggage that people think is part of sex but isn't.