I just want to add my voice to those who are saying that the spoils of the crusade shouldn't all go to the one who contributes most. It would be nice if lesser contributors received baronies, counties, duchies etc. As happened in real life. Otherwise we'll end up with the Holy Roman Emperor or the Pope (it'll happen, just wait) gaining all of Jerusalem or Spain and then handing it out to their own vassals who weren't on the crusade, while people who actually contributed to the crusade get nothing but a little prestige boost.
Generally speaking though, I think you're on to a winning idea. I think that the division of spoils might need tweaking, though.