What do you mean by "official method"? If you want a translation to another language then use/create a translation. If you want to customize just some strings of text then use the "custom" directory. The idea of that directory is just to override some strings. If you override them all then you'll lose track of what you're actually overriding and what not. Not to mention if you'are overriding everything it is highly likely that you're actually translating, right?