EU2 is much to predictable, fun but predictable, especially with your much vaunted historical events

. example
I spent the better part of a hundred and fifty years making a strong alliance with Lithuania when I was Russia. the Polish annexation comes around despite the fact the Poland and Lithuania had fought a war (In which Poland took a Lithuanian province) and their relations were -90 or less.
I had anticipated having that ally for awhile, not seeing them get annexed by their enemy. So basically you can play as Poland have horrible relations with Lithuania and still annex them.