This honestly sounds like less of an issue with the Factory or the Manifesto rule and more of an issue with individual factions going to war with each other. The Manifesto is there to help you get a general knowledge of what sort of weaponry and forces your enemy posses and in what quantity, ranging from specialized units to armadas and armies. As a character, especially one in a high position IC that being a Faction Leader can grant you, you should be able to tell what the brunt of your enemies arsenal looks like but shouldn't be able to peer into every nook and cranny and see what kind of stuff they can pull out of their sleeve from an IC perspective.
It is up to the individual faction leaders to discuss their armies during the round table negotiations of an invasion. It should be stated clearly by each side what their main forces look like, what sort of technology they have, and what their specialized units / tech is and looks like. If one side wishes to use a new unit or new technology for a surprise attack / counter-attack and there is no concrete past IC example where said unit / tech was used, it should be common courtesy to allow them the surprise with them. If however, said unit / tech has been used 20 times in the past month in large scale invasions, it should be a pretty safe bet that word has traveled to all other factions and counter-measures can be enabled. It's up to you guys, the faction admins, to properly regulate the battlefield. And don't give me any silliness about "gameyness" or something like that. You either put in the extra effort during planning or you can continue to whine, complain, and queen at each other until you end up with OOC hatred of each other.
Just as well, it's the Faction Admins responsibility to properly keep their members under a leash during an invasion. Speak with them, tell them what will happen and how it will happen and give them creative freedom to mold the event to their liking as long as they keep certain tenets in mind, don't let them go balls to the walls.
Long story short, put in the extra effort during talks and planning to make sure silly shite like this doesn't happen.