Yep. Following Bannockburn the Scottish crown invaded and held significant parts of Ireland. I find Irish history in that period somewhat confusing - there's a lot of double crossing and inter-familial conflict - but ultimately Edward de Bruce failed because the Pope refused to transfer lordship of Ireland to him (the remonstrance of 1317) and he and his army got caught up in the Great Famine of 1315 - 17, causing significant loss to disease and hunger, the need for morale and support sapping pillaging, and ultimately putting him in a position where he can be defeated in battle.
Maybe a pod is the Pope getting all anti English and agreeing to the remonstrance?
Even so, what's the chance of a peaceful occupation and joining of the nations- the Scottish army was happy to pillage and de Bruce happily burnt out opposing lords after eating all their stored provisions - there's nothing to say that Scotland would treat a subservient Ireland any better than England did
Well the monarchs, which by this point had most influence on the Papacy were the king of France and the Holy Roman Emperor. Granted the former had arguably had the advantage by this point.
England coming into conflict with one of them, might see the Papacy being persuaded by either of them to change its' opinion.
France and England had a complicated relation since the Norman Conquest of England, which lead to a French vassal simultaneously being a Sovereign of another realm. The Holy Roman Empire and England had less ties and conflicts of interest; though they might need to be persuaded to stay neutral (that would also apply to other Catholic monarchies).
Either way it's not just the Papacy, which needs to change their opinion. Scotland would need a powerful ally, which can persuade the Papacy and has a conflict with England, so this makes France the most likely candidate. Though France alone might not be enough, if England under this scenario has enough allies, then the Papacy might just opt for the status quo (ends up like OTL).