Sorry to interject here, I've been following along. Regarding the earlier subject Michael/Micha, both are from Hebrew meaning "who is like God." Michael uses the generic 'el' form of God and Micha uses the specific 'Yahweh' form of God (here shortened to just an 'a' sound).
The name in question, Mícheál, is the far and wide the most popular form of Michael in Irish-Gaelic. There is also the hypercorrected form Míheál along with a few spellings exclusive to the Old Testament of the Gaelic-Bible.
The Biblical name Micah is translated Míceá in Irish. This reduces the whole 'ch' difficulty into a hard 'k' sound, which may aid for use as a nickname. I believe it to be pronounced [MEE-kyaw].
With regards to that 'ch' discussion: I've read that the Gaelic 'ch' is roughly equivical to the German 'ch' as in Bach, though I've always personally understood it to be more akin to the Hebrew 'chaim.'