What if one decision in the story went the other way

A what-if about Fullmetal Alchemist Brotherhood. This is fan speculation and analysis, not an attempt to reproduce the author's text.

The change: Ed and Al never attempt the human transmutation. They grow up, Ed still becomes a State Alchemist at 15 for the same reasons, but neither of them has lost anything yet.
What I care about: Whether Ed still ends up against Father, and what happens to Al with no reason to be desperate
How far to follow it: the whole story, rewritten

Before you start, tell me in three or four lines what the story needs this moment for, structurally. What work is it doing? If removing it breaks something load-bearing, say that now.

Then:
1. What changes immediately. The first few scenes that go differently, one line each.
2. Where it diverges for good, and what replaces the parts that can no longer happen.
3. Where it converges back. Most stories pull towards the same ending through different routes, and the interesting question is which parts are actually forced. Say which.
4. Where it can't converge, and what that costs the ending.

Hard rule: every character keeps behaving like themselves. If your version only works because someone acts out of character, stop and tell me that instead of forcing it. That's a real answer and I'd rather have it.

What you get: The ripple from one change, where the story pulls back to its shape, and where it can't.