You can, it's how it's done, but it means someone who knows any other language using the Latin script still can't read it.
A speaker of French, Polish, German, Hungarian or Turkish can muddle through trying to pronounce another European language using the Latin script and get 95% of it but will have no idea of how to read Vietnamese.
A speaker of French, Polish, German, Hungarian or Turkish can muddle through trying to pronounce another European language using the Latin script and get 95% of it but will have no idea of how to read Vietnamese.