From working in international communities, I refrain from referencing FirstName LastName, usualy for labnels I use “Given Name” and “Family Name”. And then at least for one example, in China, most common the Family Name is listed first (a suggestion of the importance of family over the individual?, yet often you find people from the region will provide a “western-ized” name to call them by (I work with a number of Dave’s in Taiwan ;-).
And even here in North America, I know of a number of people that have a two word first name (one is a daughter).
In my own work, I do not need to necessarily have a split into first/last, but at least some way of greeting a person in communication. I can understand the limitations on changing any data structure, and am okay using a convention of parsing by the first space to extract at least a name to address someone. Perhaps the form where a full name is entered could have some kind of explanation/label indicating that the first portion is used as a greeting name?