in battles why we cant capture enemys soldiers and high valuable generals rulers it should be good feature in eu4. for example after battle of pavia spain captured france king and held in madrid, after Treaty of Madrid he relased.
http://en.wikipedia.org/wiki/Battle_of_Pavia
http://en.wikipedia.org/wiki/Francis_I_of_France
my other suggestions about rulers is, if ruler have 6 admin stats we will give them a admin bonus or have 6 diplo stats we will give them a diplo bonus, and rulers general pips should be depends their military skill, if he have 6 stats thats make him to 3 star general
http://en.wikipedia.org/wiki/Battle_of_Pavia
http://en.wikipedia.org/wiki/Francis_I_of_France
my other suggestions about rulers is, if ruler have 6 admin stats we will give them a admin bonus or have 6 diplo stats we will give them a diplo bonus, and rulers general pips should be depends their military skill, if he have 6 stats thats make him to 3 star general