I am not aware if this topic has been brought up before but I thought it would be an interesting topic none the less. When I play a grand campaign and I have progressed to the point where my immediate enemies are at bay or eliminated, I tend to engage in "state-building". I chose a faction that I like or I see could benefit me in my later campaign and give them ample funds, free technology in increments, and conquered territory. In terms of territory, I hold onto them until they have been legitimately developed and tax revenue is in the thousands. Once I deem it necessary I gift it to a faction for free or in exchange for another territory they have that is underdeveloped. All the investing I do is recouped with taxes and trade that I gain while developing said territories. But of course this can get out of hand when you find yourself continuously reconquering territory that the faction loses and declaring war on the faction's enemy to keep the fragile state together. I usually find myself fighting the faction's war for it

.
In my present campaign as Sweden I conquered Scandinavia and most of Russia's territory except for one in the far corner. The Ottoman Empire requested an alliance soon afterward as we already had a healthy trade relationship. I was all too happy to oblige in order to curtail Austrian and Polish-Lithuanian ambitions (at the time). Of course the Ottomans were having trouble so I decided to concentrate my forces in Caucasus and conquer and develop the regions there. By the time they were developed the Marathas were knocking on the back door and I found myself fighting The Ottoman's war for them. Several Maratha stacks were waiting on the border of Georgia and it took about 10 years before I wore them down enough that I could get forces down to Persia to destroy their supply line. When Persia was taken it was somewhat of an easy ride considering that between Persia and MC borders was a buffer of poor desert territory. The MC did try to hack away at my developing colonial possessions in the Americas by laying siege to the Leeward Islands (apparently all the factions wanted it, it was fairly developed), ultimately resulting in their defeat. I continued down to Afghanistan with three stacks but was forced to halt my expansion because of a series of rebellions. Anatolia rebelled on the Ottomans and they proceeded to do nothing so I had to recruit an entire army and navy from Ukraine and Crimea and send them to conquer Anatolia. A couples turns latter Mesopotamia also rebelled, forcing me to recruit another army to conquer it. Even though we both had indefinite military access to each others' lands, the Ottomans encountered difficulties moving their armies around and they started clumping in Don Voisko. Much to my reluctance I found that they needed a continuous territory to get their troops around so I gifted them Mesopotamia and Anatolia prematurely along with Afghanistan and Baluchistan for Egypt. I sued MC for peace and they agreed along with granting me trade rights worth 3,300.
Even though I gave all my technology and tens of thousands of coin to the Ottomans every so often, the computer was a very poor manager at least in the Ottomans' case. I was surprised to find that Mesopotamia, Anatolia, and Egypt were all underdeveloped in 1750 (all three had dirt roads). However, I have had better results with minor factions in Europe (probably because there is less territory). Anyways, a long story short, I was just curious if other players engaged in the same sort of "state-building" behavior as I do and what their experiences were with it?