Yes... But still. I'm sure I can found counts for you, who married characters in other places. It would be just annoying. Why not simple a distance malus for marriages? That would be better as this (from my sight) stupid region system from the start post.
One exemple:
Balian of Ibelin, a French noble, married
Maria Komnene, the daughter of
a Byzantine doux. Yes Balian defende Jerusalem as this time... But he was never a baron or count in Jerusalem. Just in France.
Many vasalls of kings of Jerusalem were at the same time barons, counts in Europe. Or sometimes important rulers there, So this suggestion was bullshit in this times:
It wasn't uncommon to hold land in different places at this time. I don't want to give my French or Greek county to another ruler, just because I'm the king of Jerusalem.
Splitting demesn was the rule in this time.
http://upload.wikimedia.org/wikipedia/commons/f/fb/Etat_bourguignons.png
http://upload.wikimedia.org/wikiped...varia-Straubing_-_Karte_Straubing-Holland.png
They mostly not has the plan to have a closed territory.