Uhm, I'm pretty sure that's wrong. Hover over British industry score at any time during the game - most of the industry score comes from super-populous and advanced England, which is never touched by wars and has enough troops protecting it. Not sure if I'm doing something wrong or what, but playing AHD + A Pop Divided mod (quite sure APD uses the same colony-to-state mechanics as vanilla) I haven't seen, at any point during any of my games, that Brits would get any industry score from their colonies, AKA they can't turn it into a state because they don't have enough accepted culture represenatives to get 1% bureacraut ratio.
And that sums it up - war, war, war. This is not just about economy when you're playing a country that isn't Britain or France (even tho France would probably need war to take Britain outta the #1 spot, not garuanteed, though). When I was playing as Prussia and then turned into Germany, all I needed for total #1 dominance, over Britain & France, was to kick the butt of Austria-Hungary (took various regions, provoked other nations to jump the opportunity & declare war when I was pounding Austria, freed multiple nations) & France (took Alsace Lorraine, then 2 regions that led to Dunkirk, so I had pretty good foothold in France, had them on 100% WE for awhile and destroyed every single one of their mainland armies, including mobilized poor fellas), afterwards everything went up - France was out of the play and so it was easier to concentrate on beating the Brits, plus the 3 French regions kinda helped in industry. The rest is common sense.
Be opportunistic, if someone is pounding France (this is pretty much the nation you can beat with opportunism, because France almost always fights with Prussia/NGF/Germany, if the latter hasn't been defeated first by Austria or someone else), you jump in and take the opportunity. Just make sure to not join too late (other nation might end its war and you'll be the primary focus of France, altho it'll be very weak if the enemy had pounded them long enough) or too early (their armies will be just freshly mobilized and they'll be ready to go attacking at you, probably defeating your armies if you're Spain).
That's what war between big boys is all about, in my opinion, unless you, of course, have a stronger or equal army to the great power, then you don't need any opportunism to beat their asses, but it sure makes it easier.