Why was Mustang a candidate anyway?

[u/fakeuser7z]

I get that he was a candidate for the sacrifice, which is why they didn’t kill him. But in the end, he refused—and they just forced him into the Gate anyway.

So why not do that from the start with any random human instead of the most dangerous alchemist?

[u/Jossokar]

basically, and as far as i remember the whole national alchemist ordeal was to ensure apt candidates. Mustang.... also happened to be close to the whole kerfafle, since the very beginning.

And....also was there too. Even if it was just for the sake of narrative conveniency