It would be beneath him to cheat.
彼はごまかしなどできる人ではない
It would be best 「for you to start [that you should start] the work now.
今その仕事に取りかかるのがいちばんよい（◆叙述用法ではtheをつけないのがふつう）
It would be better still not to produce it.
それを生産しないことの方がいっそういいと思う
It would be inappropriate for me to comment on the matter.
その件に私がコメントするのは適切ではないだろう
It would be prudent to leave doctors' business to doctors.
医者の業務は医者に任せておくのが賢明だ
It would be rash to conclude that ....
…と結論づけるのは無茶だ
It would be suicidal to offer it.
そんなことを申し出るのは自殺行為だろう
It would be to his advantage to learn Chinese.
中国語を習うのは彼のためになるだろう
It would be worth his while to talk [worth while his talking] to the boss.
彼が上司に話すのはむだではないだろう
It would seem that he has lost his keys.
彼はかぎをなくしたようだ（◆it seems の控え目表現）
