Earlier quoted context omitted.
"As a French" ne veut rien dire en anglais. Il faut rajouter man, person ou quelquechose. Frenchman, French person, French citizen.
The demonym for France is "French," so it's not wrong (even if it doesn't sound right.)
Yes, languages can change, but there is no evidence that native speakers have started saying "a French". The only context I've ever seen that in is "As a French...", which strongly implies a non-native speaker of English. The evidence suggests that it's a common language interference error from French, not some future development of English.