Many of us are fully aware that this results in a non-grammatical use of the second person plural form of the verb to be with the first person singular pronoun be we have gotten used to it.

Sort of. My mother often used "amn't" in a joking manner (pronounced with all the letters, since we are in Canada) and I occasionally use it in informal conversation. I got a strange look from my Turkish friend for using it the other day, though. I have mixed feelings about it. If I were to write it I would use the "proper" form which I consider to be "Aren't I?" I'll admit that even that looks awkward, though...