It was
discussed relativly recently. Allow me to repost my previous contribution, with some additions and modifications.
Imagining that both Raimond of Poitiers dies earlier (the guy was quite unskilled, as he managed to piss on both basileus and the poulains, while not as such than his successor), with Michael I maybe forced to go on an expedition against him (with the agreement of the kingdom of Jerusalem) and that the reconciliation of 1150 holds, with Alix being actually a boy.
It wouldn't be surprising to see Aquitaine, or at least Gascony, being trusted as an apanage (a land of the royal demesne being trusted to a member of royal family, theorically turning back to the royal authority if the line fails). The disorders in Tolsan would be greatly changed as well, as the counts of Toulouse couldn't count on Capetian support as IOTL, as Capetians would be the claimants on the county, not Plantagenets.
Maybe a more direct, and more quick Capetian control over Languedoc?
Or maybe Raimondins would try to turn for Aragonese support? That would be a great diplomatical shift, but giving the circumstances...
It would have interesting local political development, with Trencavel and House of Aragon still relativly powerful there. It may influence how Catharism would be harboured : maybe less so than IOTL.
A greater occitan influence on french court isn't to be dismissed (and may be likely), even if Alienor would probably have the same reputation than Constance of Arles as a queen. As in, bad but with a lasting legacy.
On Plantagenets,their political influence would be greatly reduced in England. Controlling and hoping to controll half of a kingdom isn't the same thing than being a former ennemy with control over Maine and Anjou, and doubtful control over Normandy.
It may be too last for Stephen to change his politics, but clearly the political advantage of Plantagenets would be reduced. Remember that the treaty betwen both sides was signed only in 1153.
As the death of Eustace of Blois is certainly not a given with a PoD in late 1140's (or the death of Stephen), you'd still have a legitim heir for Stephen before 1152 and it's likely that the control over Aquitaine and the greater prestige of Henri played fully IOTL.
Would be able to hold the claim on England and enforce it? I'm not too convinced he would.
In the contrary case, it doesn't mean Angevins wouldn't have a political role to play, but it would be more akin to the House of Blois in Champagne and eastern Francia.
With time, depending on the events, you could have a lasting conflict and division between English and continental holdings.
Maybe a lasting Blois-Flanders-Angevin opposition to a Norman-English circle? (Likely) Capetian intervention (probably on both sides) may proove interesting.