Thanks for the map!
Norfolk is an enclave - it is cut off from the rest of Percy holdings by The Wash. It only can be reached by boat without going through Mortimer's lands. Is there some human geography behind awarding it to the North?
No idea. given that most of the wealth and population of England are in the south I suspect it's supposed to be some attempt at an equal split on those grounds.
Another question - does Wales have an archbishop? Having a churchamn of that rank under one's control was highly conducive to independence. One of the reasons for Poland and Hungary retaining independence and Czechia becoming part of HRE was the possession - or not - of an archbishop. But that was 1000-1200 stuff, so maybe in 1400 things are different.
No, although obtaining one was a goal of Glyndwr's (or reviving to be more precise, St David's was usually regarded as an archbishopric from the time of it's titular saint until the Norman conquest of the area in the 12th century) - he went so far as to back the Avignon papacy during the schism that was going on at the time in the hope of getting French support, but the war took a turn for the worse before this could happen.
Prince of Wales - with a docile archbishop he can crown himself King of Wales.
Probably not a problem -the Welsh bishops tended to be a fairly wayward bunch...
The map isn't showing a Percy Northamptonshire or Warwickshire either.
Tbh I've not seen an accurate map on what the Indenture was. Look at this version:
That's from the Wikipedia article, which unfortunately doesn't match up to the words of the article, which says -
Northumberland was to have received the north, as well as Northamptonshire, Norfolk, Warwickshire, and Leicestershire. The Mortimers were to have received the rest of southern England.
The four named counties are included in the pink area on this map not the blue, though they are assigned correctly in the earlier map.