I don't understand the outrage over singular "they". I agree that it's not particularly logical, but what part of the English language is?? It sounds natural, at least. It's certainly widely used, and will likely become a "correct" form within a few decades.

The OP suggests guessing gender from names. There are too many unusual cases and gender-neutral names to be able to guess gender from a name alone. Even ignoring non-english-speaking world, I know several guys named "Kelly" and "Kim" and I have a female cousin named "James" (she goes by "Jill", though).

Adding a gender field is often not feasible and a bad idea for other reasons (gender identity, etc). It's far better to sidestep the issue with commonly-used-but-not-quite-formally-correct grammar, i.m.o.