Disgusted as I am by that Wessex yet overjoyed as I am by Yorkshire and the Humber's new name, I shall be presenting in further detail the proposal I outlined on the other thread. All talk of new constitutions on one hand, and of unwritten constitutions and political constitutions from overrated twerps who think they're far smarter than they actually with a Twitter following largely consisting of idiots convinced they're not on the other, ignores that England already had a constitution which should be restored as much as can be reconstructed and is practicable.
The English
cyning, despite much confusion due to the usual mistranslation, was a head of state with wide-ranging powers, yes, but one who was most importantly elected and is better likened to a president than a monarch (as conceded to me in an argument with some 'unbroken continuity' pseudo-reactionaries earlier this year). The constitution as it existed before that most tragic of years therefore already offers a perfectly good solution: a head of state elected by some sort of electoral college.
Powerful as this president--as I will refer to him (as they all were, though Eadgyth's election was prevented only by her unwillingness to take the presidency) henceforth as a significantly better translation than the usual one--was, and I will note that it is little different to the power of the American presidency, the government of England was not his alone. From the unification of England by Athelstan national assemblies were routinely called, with representation from all sections of society, and also had a significant role in governance. And, likewise, as strong the English state was, so were the lesser tiers of government, down not just to the shires but to the hundreds (and their analogues). You might look at that as being a function of the former.
This model seems seems perfectly appropriate for England today. A representative national assembly with no permanently-set location, travelling the country and temporarily co-opting members by sortition. And there is no need for the regional assemblies long demanded by some, but rather strong local government with the realities of governance in mind instead of Yorkshire irredentism and other such nonsense.
England should also return to its pre-Norman borders. But not only William the Bastard should be held to account for the partition of Middle Britain: unfortunate as it will be to lose both Edinburgh and Glasgow, Scotland too must recognise its own voluntary involvement in this and return those Cumbrian and Northumbrian territories to, respectively, an independent Cumberland and an autonomous Northumbrian state in association with England. While the basic geographic realities of Britain should be recognised and a common defence and foreign policy in place, again there is no need for anything more.
I participated in an AH.com project where we built an election map for an alt-UK that had Ireland still included.
So that's who you are. I briefly participated in it at the request of the OP, but alas all I contributed were some mediocre Irish party ideas and some suggestions for names of proposed constituencies local to me.