The main problem of NTW's campaign (at least for me) is that when a major power declares war on one of your allies/protectorates, the only way to "save" them is to obliterate the major power yourself. Even if you maim the major power and then make peace with them, nor them nor your protectorate will ever sue for peace with each other, so if you interrupt your pressure on the major power, your protectorate will be left alone to fend for themselves, and will eventually succumb.
On the other hand, if you start completely obliterating major powers knocking them out of the campaign, it becomes boring fast, with no one really able to challenge you as you steamroll everyone else.
I actually just found something that may revitalize the campaign a little.
First of all, never take any major power's capital before you took all their territories (this is not a matter of realism, as much as a practical matter). When you finally get to capture the capital, just liberate it, that way it'll be turned into your protectorate. Give back some of their territories as well.
This simulates quite well a realistic treaty like those made during the napoleonic times. Defeated major nations didn't get completely cancelled from the map, but paid war repairs money (which is simulated by the protectorate income) and had to give some of their initial territories to the winner (which is simulated by the regions you don't give back). Depending how much you like a challenge, you can give them back more or less regions (more, more challenge, less, less challenge, obviosuly).
To add further realism, you may want to give one region to protectorates/allies that helped you the most during the war, or that were attacked by the ex major power.
The added bonus of this is that the diplomacy of the major nation you just defeated will be completely reset, and they won't be at war with anyone anymore, saving your allies/protectorates from retaliation, at least for a while.
The good part still has to come. Major powers act in a rather peculiar way when they are made a protectorate. While minor protectorates usually stay put and follow you around like puppies, major powers will just rebuild their armies and economy and eventually will declare war on you or on one of your allies/protectorates to regain their lost territories, breaking the protectorate status and giving you another challenge down the line
Personally i found that this adds a lot of depth to the camapaign, and helps avoiding that state of utter boredom that tends to be a killer towards it's second half.
You can even take a few turns to make sure that the "new" major power is well fit for war before giving their territories back (this simulates temporary occupation), for instance I make sure that they at least have one commercial and one military ports, at least one barracks and one cannon foundry and so forth. It's amazing to see how badly some nations build their economy up, and how they never, ever convert buildings to a different use than what they were initially chosen for.
This adds further to the challenge, as you get a nicely outfitted enemy, that will field warships in battle, and not only indiamen, and so forth.





