would have done的用法？

Question

我倒觉得慎重考虑没有坏处。（《唐顿庄园》原台词）
Actually, I thought a little sober reflection would not have gone amiss.
这里问什么用would have done

Answer 1

Actually, I thought（then） a little sober reflection would not have gone amiss(before then).
Actually, I thought（then） a little sober reflection would not go amiss(after then).
动作的先后顺序而已
would have done 表示对一件事情的判断。 和 虚拟语气没一点关系。

Answer 2

是虚拟语气用法，表示与过去的实际情况相反。

Answer 3

thought和would是对应的，都是过去式
would not have gone过去将来完成时

Answer 4

虚拟语气的用法，具体句子具体分析。

Answer 5

虚拟语气，表示与过去事实相反。