I have to agree with the above. In all likelihood what happens is (either straight away or after a few generations) the Kings of Ireland intermarry with the ruling Irish Kingdoms, lose their Angevin/English heritage and become part of the establishment, as happened when Strongbow first invaded. In all likelihood the strong King position would eventually disappear too as it would be merged with the part-elective part-military-strength tradition of the High Kingship, and in 100 years Ireland would likely be back to its former position of having a number of vying states and no clear King.
Of course this could be avoided if the Kings of Ireland can rely on English aid to keep their position intact, but if that happens, the Kings (of Ireland) will face hostility from the Irish petty Kingdoms, who will resent the idea of foreign imposition, and so they will likely be far more unruly and harder to control, at least for a few generations.
Yes, Ireland has a lot of places hard to get into (i.e. rough country, forests, swamps) where people can hide out from central authority then emerge once the troops are gone. There's got to be some reason it's better to obey the central authority than strike out on your own.
Hmm. Would the Norman Crown disappear that quickly?
The Lordship managed to survive quite a while though steadily reduced.
Would having a King on site (as it were) mean a larger Pale?
I see an analogue with France of the early Capets with the Irish Kings being the autonomous Dukes.
John was notoriously treacherous and would have intrigued to take the English crown from his nephew if there was ever an opening. This might backfire. There's a decent chance that John would have offended the Normans in Ireland, the native kings (see below), or both, and that some combination might offer the crown to John's nephew.
[When Henry II had sent the young John to Ireland as his representative, he had irritated the native chiefs by pulling their long beards.]
Who is available for John to scheme with?
But if he does try, and fails, his crown would likely go to his sons and we're off towards what Falastur described.
Assuming we end with a High King model under a FitzJohn King with Irish Earl-Kings and Norman-Irish Earls of Waterford, Ulster, etc, what impact can we expect from outside?
Would the Irish King interfere with the Kings/Lords of the Isles v Scotland v Norway?
What are relations with Wales like? Irish support could provide an independent Welsh Prince/Kingdom.