I don't like names that start with I if it sounds like the pronoun. And
Isaiah is very much an old man in handmade sandals, toiling up a desert hillside. Also, where I live we say ie-ZIE-a but I believe it's usually ie-ZAY-a in the US - is that right?
Isaiah Christian is biblical all right, but if you're either
Christian or Jewish, why not? If a child named
Isaiah Christian doesn't come from a religious family, people might be confused for a while but they'd learn to cope.