I was thinking that due to their small size (and as you say the drastic increase in sieges) that none would be required - the settlements are too small to warrant fortifications per se. Possibly walls and gates, but the gates are open. The defender gets the typical city defence but there is no weary prelude. If the attackers win the settlement is razed automomatically.

Yup, I'm back. Been dipping in and reading a lot about mods etc etc but havn't bothered writing as I've not been playing enough to have any valid input.