Ok so that's not a great solution. Is there anything we can do? Maybe something to give France a reason to hold back? Upping the fear the young king has of his rebellious vassals? I know there are people who say France doesn't invade Iberia in their games but I've tested it, and I've started a dozen games and every single time France goes straight for Spain. Granted I'm sure 100 years down the line the random variations kick in and sometimes France will lose, sometimes it'll fall apart, while it's never happened in one of my two proper games so far I don't doubt that will be the case some times, but shouldn't France be less gung-ho about invading Spain right from the start in the first place? I'm sure there's a simple solution that will keep everything as it is except for France invading Spain at the start.
As RedRooster mentioned, Toulouse and Aquitaine should be independent at the start, which would solve a lot of the problems related to the blue blob.
I was a pretty vocal proponent of that being done, during the beta. However, there were those who strongly disagreed with me, and it remains the same. Will I mod it in my own games? Yes. Although, I'm giving CK2 a little bit of time to evolve post-release before I worry too much.
This is the real problem, there really isn't a reason for France to keep out of Iberia. When I play someone in France(Duke or King), my day one opening move is always to attack the weak northern muslim states. If we find a good gameplay mechanic to keep France out of Iberia, it would be simple to wire the AI to do the same as well.
Gameplay mechanic wise, the reason that the French stayed out of Iberia, was because they had much more difficulties closer to home for the first couple hundred years. There is absolutely no reason at all, whether logical or historical, to keep a strong and unified France (as shown in 1066) from marching over the Alps. About the only gameplay mechanic to affect it would be the general nature of attrition, army mobilization and retaining foreign lands being as easy as it is.
But the basic reason why our illustrious 1066 French forebears did not set up a Franco-Iberian empire in the 11th Century was because the French Roi was still dreaming of the day his authority would even be imposed on the Occitan world. Something that didn't really happen until the Albigensian Crusade, centuries later.
But so long as there is determination to keep the duchies of Aquitaine and Toulouse as direct vassals of the French Roi at game start, this will stay as is. Since doing so basically removes a hundred and fifty years of struggle. With Burgundy as well, I might add, which persisted past even CK2's time frame.