I used to play French a lot and I found a unique strategy of trading one space for another. I took out the English provinces. but not to keep the lands, but to eliminate the English as a faction when stage two is done. Stage two, I build up some extra troops, then deconstruct most of the buildings in France for the gold. I mass all, and I do mean all, my troops in Flanders and then invade and crush all of England, including Wales and Scotland. In the meanwhile, the Germans generally go crazy and invade my french lands, but it is ok, for as long as I can hold onto Flanders, I am ok. Now, I convert England into my new "base." This way, I lose the farming revenue of France, but I need only worry about defending Flanders, and then I can building up my trade-links, and so on. Once I bring Ireland under my control, I have all I need to smash the HRE out of France. The idea is simple. I trade rich but hard to defend France for poor but easily defended England. England doesn't have the resources for me to conquer the world, but it does have the resources for me to reclaim France and then the world.
The advantage is protecting your infrastructure, by placing your production centers in England, out of harm's way. There is just enough money in England to fund a reclaimation of France later, and once you secure France, you have all the money you need to conquer the world. You will be able to concentrate on building soldiers and farms, not protecting your production centers. As long as Flanders is in your hands, the door to England is closed, if you fail to reclaim and hold onto France, you can just try again later