Some events on similar lines to MattyG's for Wessex.
The Grand Duchy of York - parallel to the Principality of Wessex:
The English crown - as above, but with a proviso that Wessex hasn't already had the event. It's unlikely, but possible, that one country could claim to be England, the other could revolt away and annex its former rulers and then have them revolt away - this could lead to Malborough or Wellesley fighting himself. 
This event will probably trigger Scottish annexation of York if they haven't already managed it by 1670. The B choice will make Scotland angry instead - I'd suggest a 2 choice event triggered for them: either go to war for it (immediate WAR or a CB, plus added cores?) or accept Elizabeth and re-vassalise. If they go for war, I think Scotland should get a "Sultan becomes Khalifa" type immediate annexation if they capture Yorkshire.
The Grand Duchy of York - parallel to the Principality of Wessex:
Code:
# York Becomes a Grand Duchy #
event = {
id = 406110
trigger = {
owned = { province = 240 data = -1 }#Northumberland
owned = { province = 244 data = -1 }#Midlands
countrysize = 5
atwar = no
}
random = no
country = YOR
name = "The Grand Duchy"
desc = "Once upon a time the Percy family were one of many nobles vying for dominance in England and kept in the shadow of Scotland.
That is no longer the case: York is henceforth a Grand Duchy, clearly one of the principal powers on the Island of Britain, no longer under any foreign suzerain."
action_a = {
name = "Excellent"
command = { type = badboy value = 1 }
command = { type = DIP which = 1 value = 60 }
command = { type = vp value = 100 }
command = { type = breakvassal which = SCO }
command = { type = breakvassal which = EIR }
command = { type = breakvassal which = BRI }
command = { type = breakvassal which = HSA }
command = { type = breakvassal which = NOR }
}
}
Code:
# York Claims England #
event = {
id = 406112
trigger = {
event = 406111
owned = { province = 247 data = -1 }
owned = { province = 249 data = -1 }
stability = 1
atwar = no
NOT = {
vassal = { country = SCO country = YOR }
exists = PUR
event = 405010 #Wessex already has made the claim
}
}
random = no
country = YOR
name = "The Resurrection of England"
desc = "After too long in the shadow of Scotland, The Grand Dukes of York have taken London while crushing their rivals in the West Country and are close to achieving that goal that their ancestors first set out to achieve: the Kingship of England.
Of course, it would certainly cause consternation to our Celtic neighbours if such a claim were to be made.
My Lord, shall we therefore claim once again the Crown of England? The people and nobles are tired of being ruled by Bretons, Germans and Scots."
date = { day = 1 month = january year = 1450 }
offset = 90
action_a = {
name = "Northerners We Are and Northerners We Shall Remain."
command = { type = ADM which = 1 value = 120 }
command = { type = DIP which = 1 value = 120 }
command = { type = MIL which = -2 value = 120 }
command = { type = domestic which = centralization value = -1 }
command = { type = relation which = SCO value = 150 }
}
action_b = {
name = "To Westminster to Receive the Crown of England!"
command = { type = addcore which = 240 }
command = { type = addcore which = 250 }#Is this already a core?
command = { type = badboy value = 4 }
command = { type = relation which = HSA value = -50 }
command = { type = relation which = BRI value = -200 }
command = { type = relation which = EIR value = -200 }
command = { type = relation which = SCO value = -200 }
command = { type = MIL which = 2 value = 60 }
command = { type = DIP which = -2 value = 60 }
command = { type = ADM which = -1 value = 60 }
#Won't we need York versions of these with different IDs?
#command = { type = wakeleader which = 34961 } # Malborough
#command = { type = wakeleader which = 34966 } # Wellesley
#command = { type = wakeleader which = 34976 } # Nelson
}
}
Code:
# The Last of the Percies - Scottish Claims #
event = {
id = 406112
trigger = {
vassal = { country = SCO country = YOR }
}
random = no
country = YOR
name = "The Last of the Percies"
desc = "The last male heir of the Percy family who have ruled the North of England as Earls of Northumberland and Dukes of York has died, leaving only a daughter, Elizabeth. Title to all the Duchy's lands is being claimed by the Scottish crown."
date = { day = 20 month = May year = 1670 }
action_a = {
name = "Accept Union with Scotland."
command = { ###trigger a Scottish event to annex YOR ### }
}
action_b = {
name = "Long live the Grand Duchess!"
command = { ###trigger a different Scottish event ### }
command = { type = breakvassal which = SCO }
command = { type = relation which = SCO value = -200 }
}
}
