definitely getting honour and land bonus for war win is a good start. Even if it doesn't encourage them to whore it should have successful kingdoms stay in a larger land tier together so you don't end up warring weak kingdoms for your first 3-4 wars.
ability to use pool in eowcf also i think made it easier for war kingdoms as naps were less important and it made it easier then land dropping to get similar size spread. Mind you land dropping continues to really never be necessary and a cowards way to face easy opponents.
Still if you're gaining minimum 5k acres for each war win that would have the top war kingdoms all around 90-100k end of age leaving the weaker kingdoms at 40k to be safe :)