The last sign-up system I built you get a single max length utf8 field called 'Name'. This field is not used at all in the UI except on the profile screen where it appears in full and in email templates where it also appears in full. It might not be perfect but it's as good as you are going to get without having to become an expert in names. I'll leave full localisation to companies that can afford to dedicate a team to it.
In my university (TU Delft), there are people from all kinds of countries, so they have a (I suppose legally-mandated) first name / last name entry, but also a "How should we call you" entry, in which you can write anything you want, and that's what will appear in the UI and class lists.
