To me it seems rather inefficient since it takes like 450 days to prepare 1 collaboration government if you use spies plus boatloads of support equipment due to needing multiple missions for 80% compliance.
I see, i just tried to do it with Iraq as Portugal but i guess that ain't that good of a target? I know that your Macau part of China becomes 80% compliant long before you start changing ideology as Portugal, and then it gets cores on all of China, useful if you take out Guangzhou with all that steel and manpower, gives you a nice staging point for the rest of China. Then you can expand your China a bit and take Tsingtao too for that treaty port prestige.When you want to attack a major ( like USSR ), it's very helpful to run collab-missions with your spies, before launching the assault.
Each successful collab-mission will decrease the sum of victory-points you need to let them capitulate.
Playing Germany I reduced the sum to 70% ( so I didn't had to take Wladivostock, Irkutsk or other victory-points in the far, far east of USSR )
To me it seems rather inefficient since it takes like 450 days to prepare 1 collaboration government if you use spies