So I've been having a think, and I have a few thoughts I want your opinions on.
Brythain is divided among the Lûith and Cynn (British clans and their A-S equivalent), the leaders of whom are chosen by the Âlt Rî. Those leaders select deputies with the Âlt Rî's approval. As has been said previously
The clans are further divided by class; Nobles (from whom the leaders are picked), freemen (who often serve as deputies), bondsmen, and slaves. Rough ratio I'm thinking of is 1:8:10:4. The bondsmen and slaves are split fairly evenly between freemen and nobles.
The clan leaders and their deputies are responsible for the administration of law and justice. A bondsman can appeal a deputy's decisions to the leader, and freemen can further appeal to the Âlt Rî himself, if he can bear the time and expense.
Clan leaders are also responsible for ensuring that the freemen are armed and trained for military service for at least a few months in a year, and bondsmen at least one day in a year.
For the military, I was thinking that near every man are mounted infantry, and that the Brythônys specifically keep small and strong ponies to do accomplish this (like
Exmoor or
Dartmoor), setting aside large chunks of land for the herds.
I was also thinking that a rather large portion of their army could be archers. I don't know if the 7th-8th century are too early for "welsh" longbows to become a common unit, though I don't think it's beyond their ken to do it. And given that armor is fairly uncommon for the majority of the armies in this period, they should be reasonably effective. and even against mail, a powerful enough bow with the right head can get through.