it would do him/her
Mais ça lui ferait peine, et je veux pas la priver.
But it would upset her, and I don't want to deprive her.
— Manon des sources (1986)
Ça lui ferait du bien de voir son petit-fils.
It would do him good to see his grandson.
— La Cité des hommes (2007)
Qu'est-ce que ça lui ferait que son enfant soit gâté ?
Why would it bother her if her child were spoiled?
— Une journée particulière (1977)
How would that make him feel?
Oui, c'est ça, ça lui ferait du bien.
Yes, that's it, it would do him/her some good.
— Les Quatre Cents Coups (1959)