Concerning the name medieval technically means between the fall of Rome and about the enlightenment however it is normal associated with period between the rises of mounted knights at hasting in 1066 around the 4th or 5th crusade so whilst it is technically correct it is not thought to be. I think Dark Age might be better but I don't it.
Feudal I believe is the system of government associated with William's combination of Norman and English land laws in 1066
Better perhaps would therefore be "Anglo Saxon England", "Anglo Saxon Briton", “The heptarchy”
What about Briton: Dark Ages?
I think a constant naming scheme using ether areas or towns names should be used I would suggest towns would be easier to verify (you’d also take the shire off of Nottingham and Lincoln) preferably place with a castle or cathedral prior to 1066.
Ok I think I agree with that. I'd prefer going with towns because that pesky "shire" takes up a lot of room! For the most part I have been trying to pick Castles that pre-date or arrived right around 1066.
The division wales and England should follow Offa's Dyke... The border of Flintshire should be moved west to better approximate the actual boundary of Offa's Dyke.
Ok, that shouldn't be hard to change.
The northern most Saxon rule is suspiciously Berwick on tweed’e
The kingdom of Strathclyde would have controlled the regions named Carlisle, Cumbria and Lancaster beyond the existence of Northumbria
I'm not so sure about adding another bonus up there. Is there a major castle that would be associated with defending Strathclyde?
By taking ~ 655 it would be reasonable to establish a Cornish contented of Exeter, Devonshire and Dartmoor.
Again I'm not so sure about adding another bonus. If I added a Cornwall region I would want to add Somerset and Dorchester. Part of the structure of the map is that Castles lie in the center of bonuses rather than on the borders. I want castles to be able to retaliate against border strikes, rather than defend them immediately. I'm sort of designing this map with trench gameplay in mind.