Well, i started out by dowing an indian minor, that had very high relations with GH and Kasak horde, meaning, they would join. Vassalized Kasak horde in a hurry, followed by that indian minor, and then moved to Golden Horde. Conquered all the way to Astrakhan, and Poland then DoWed together with Muscowy. That was cheap, because GH army had been kind of totaly screwed by me (who had been already at 10 years or so at war). He starts taking all western provs because they were defenseless, and i, to counter this insane abuse use Shah Rukh to steal sieges (which is totaly permited, see rules).
Resuming, when i end vassalizing GH as i wanted, i am called a cheap bastard that abuses exploits. I dowed GH Long before either of them, and had intention of vassalizing them (together with the indian minor and kasak horde). I do not see what is the problem of this. In any case, Poland and Muscow should have think twice before dowing me (if they didnt, they could peace GH). Now i refuse to give land that belongs to my vassal. I wasted too much cash on this "SP venture" like Sterkarm said, to simply give up the vassalage, just because they dowed AFTER i did.
Lastly, i did NOT abuse the game engine, since it was my intention to vassalize them long before the war ever started. Not my fault that Poland decides to dow them out of thin air (when they have already been beated by me).