How to fix the Normandy Problem

[Caeserion]

One thing CK2 does not model well is the conflicting oaths of fealty many nobles took in the medieval ages. This is best exemplified by William the Conqueror and his descendants. They were independent Kings of England but they were also dukes of Normandy and as such paid homage to the Kings of France. The game is hardcoded so that a ruler can't be both independent and have a nominal liege or two lieges or anything except one liege and independent status.

So how do we fix it? Homage is vague in texts but I wanted it to have real consequences. So:
1) William pays the King of France a percentage of his income gained from the duchy of Normandy and its dejure vassals.
2) The King of France loses the -25 opinion malus unless ambitious or proud (ambitious because he wants it anyway and proud because he expects homage).
3) There is a small prestige hit because you are a king bowing to another king. Not sure about any numbers here.
4) You do not pay taxes for any individual counties you own. You do not pay if you or one of your vassals does not own the duchy title in question.
5) If you grant the duchy title to someone else then they get the choice to pay homage. Whether or not they do depends on which king they like more.
6) All payments are terminated in the case of war between the two kings.
7) You must actively choose to pay; default is that you won't.
8) Dukes paying homage will not have their duchy drift into their actual liege's kingdom because homage is an acknowledgement that the duchy belongs to the original kingdom.

Thoughts?

 

[Lithu]

Interesting, but not enough incentive to pay homage.

Also, this wouldn't fix the "Burgundy problem" (two different lieges)

 

[Brods]

I like this. What if a someone who holds the de jure title (like Kingdom of France holds over Normandy) can demand homage from another ruler who holds his de jure lands?
Likewise you can offer homage.
And in the case of Normandy and others in their situation, they will start out paying homage because they went from vassal to King over foreign realm.

Homage gives legitimacy (prestige) to the King who recieves it, a little tribute of ducats, and creates a non-aggression pact between the two realms. The latter part may be a good incentive to pay homage, as you could hold good lands in Francia without being threatened by the big blue blob.
Breaking homage when in one should worsen relations with the de jure King, and all his vassals (prepare for war).

With this system small states could exist within and on the borders of giants, without being consumed. For example a merchant republic recognizing the authority of the neighboring Emperor, but both parties see the benefit of the increase in trade.