Thanks, good to know that you still can emphasise the subject pronoun by adding the copula. If should then be possible for the other pronouns too: אֱמוֹר לָ֫נוּ, אַתָּה הוּא הַמָּשִׁיחַ tell us, are YOU the Messiah? or אֲנִי הִיא הַתַּלְמִידָה הַטּוֹבָה בְּיוֹתֵר בְּבֵית־הַסֵּ֫פֶר Me, I am the best pupil at school.
Galivan's example sounds to me like something that people might say, but will sound a tiny bit awkward to my ears (like something that might be said spontaneously, but not if the speaker had a few seconds to arrange their thought). Note that it won't really serve to semantically accentuate אנחנו if you don't phonetically accentuate אנחנו; and if you do accentuate it phonetically, it works just as well without the copula.
Having said that, your second example (אני היא התלמידה...) sounds much less awkward to me, and your first example (אתה הוא המשיח) actually natural. I don't know why these differences, and maybe I'm imagining.