We have a particular member that will post late at night when mods aren't around, his posts can at times be inflammatory. It would be useful to be able to put him in to moderation automatically between certain times, is this possible?
No, this isn't possible. An add-on would be needed. (I don't think one exists).
I think this would be a very niche requirement. If this person is consistently like this then warnings with the threat of permanent moderation or even banning is what's required. I don't think significant changes to permissions and moderation are justified for a tiny minority. They need to modify their behaviour, not forum software cater for their failings.