The committee met and discussed whom to appoint to the post.
- “Committee” as an organization or group is usually translated as 委員会 (いいんかい), and the members of the committee are 委員. You cannot say 委員会が集まり or 委員が開かれ. The doer of 集まる should be human beings or natural objects (e.g. 落ち葉が風で集まってきた = Fallen leaves are naturally coming together to one place due to wind), but 委員会 itself cannot 集まる.
- ポスト and 役職 are interchangeable. But I personally feel that the loan word ポスト sounds a bit like a gossip talk.
- I definitely prefer 話し合った to 論じる. The meaning of 論じる is much closer to “to debate” or “to argue (like an impeachment or in order to enlighten the public)” with the nuance of criticisms or hostility. If the judicial committee of the US Senate discussed on the next judge of the Supreme Court, maybe 論じる fits because Republicans and Democrats always fight over the replacement. On the other hand, 話し合う is a more amicable and cooperative way of discussion.
Note: I’m NOT saying the original Japanese sentence is wrong or sounds unnatural.