NerfCothons
Warlord
I don't think there are enough possible military bonuses to come up with another military civic, and historically it also becomes problematic because going into a different level of detail also raises questions about the other civics.
I see Pacifism as an opt out of what the Military columns as a whole represents, similar to how Secularism exists in the Religion column. I've also seen the problem of Pacifism as a strict concept not really being applicable to history in the scope of DoC. However there are countries that deliberately reduced the capabilities of their military and remain sceptic to its use as a tool for anything other than self defense, most notably Germany and Japan. Pacifism may not be the correct word to represent that outlook, honestly I mainly chose it because it has a clear meaning in the context of this tree and already existed in BtS.
I briefly considered other names such as Non-Interventionism (too long) or Self Defense (maybe?) but didn't find them satisfying. If anyone has a better idea to name such a civic, I am open to suggestions.
By the way, I also plan to associate additional stability bonuses for defensive pacts with such a civic.
If you're trying to capture modern Germany and Japan then my issue is partially with the name. According to google pacifism is: "the belief that any violence, including war, is unjustifiable under any circumstances, and that all disputes should be settled by peaceful means." There isn't really a country that follows that ethos when applies to their military (maybe Costa Rica, but since when have you let the Mayans dictate anything?). It also sounds like that isn't the idea you are getting at, so what does work? We can always turn to the German language for short single words to explain such concepts. Wikipedia suggests Katastropheneinsatz; it really rolls off the tongue. Kidding aside it sounds like you're getting at the concept of international reliance. The belief not that all war is inherently wrong, but that there are other people more eager to do the fighting so let's let them take care of it. Self-Defense works although it doesn't really capture the other half of the concept which is that the military is only for self-defense. NATO calls its role "Collective Defense", maybe that will do.
Gameplay-wise, I think you might be able to take the stability bonuses for defensive pacts even further. What about -2 happiness for having no defense pacts but +1 happiness for each defense pact?
I also think Mercenaries could use some help. Upon recruitment mercenaries get a 2g cost promotion. Could they also get some experience to help them be more useful in the short term? After all it's not like you're going around grabbing farmers and asking them if they would like to be paid to fight. Would it be possible to give mercenaries an extra two experience (with the expectation that combined with the three from a barracks new mercenaries would start with two promotions)? Or could you have mercenaries just start with a fixed five experience regardless of the building city's infrastructure (which shouldn't affect newly hired mercenaries anyway)? This should allow mercenaries to be a better solution to short term wars or emergencies.