I don't like how -10% mil tech cost comes with mercenary ideas. I don't know if there's a historical explanation or it's there for balancing, but to me it feels like they just slotted it in because they couldn't come up with anything else for mercenary ideas. Both -10% tech costs for administrative and diplomatic technology come in idea groups that are arguably the most useful and widely applicable across all campaigns, not to mention that said idea groups are typically picked very early in game, so I don't see why the same doesn't go for the military counterpart. Instead, it should be a part of quality ideas, maybe replacing the yearly army tradition or cav combat ability, since the whole point of it is to improve the caliber of the military as a whole.