Why do you assume 6/6 leaders are easy to get? Has there been anything to indicate that it is?Again, i can not see what is so good about Offencive. Defencive is definitely better for underdogs since it makes it so much harder, slower and more costly to goble you up, while offencive gives you only a slight edge. If you fight a lot of wars, leader bonus is irrelevant since you will get same maximim quality leaders. Forced march and manuver require you to actually win battles in the first place. Prestige bonus is useless unless you can fight a lot of wars, and actually win them, but then, it largely makes leaderquality bonuses irrelevant ue to high military tradition.
So really:
-weak treatened nation=pick defencive, and grow stronger while your evil enemy goes for someone else or drains so much resources taking your land, somebody eles will backstab him.
-Strong power that needs a bit of extra punch but will only take one military idea? Quality or Aristocracy is for you, since Quality is the most powerfull single idea, and will help with navy, and Aristocracy will help you with diplomacy and will make you less of a preferable expancion target due to core cost.
-weak in manpower nation= get admin ideas to boost the merks, and invest into military tech.
-military focused= get aristocracy, since it is powerfull early(cavalry) and will give you extra full military NI group over time.
Offencive is only good as second military NI.
25% manpower and force limits is great for any nation, especially those starved for force limit for one reason or another. 10% discipline is also great.
I do agree that Offensive is worse than Quality. I do not agree it's worse than Aristocracy though; the choice between those two is very much situational.
Defensive mostly won't actually help you win battles, nor does it give you more manpower or force limits, so that again is very much situational.