Doesn't change the fact, that it still could be posislbe to find schemes of Viper Gear.
All the schemes for Griffin, Bear, and Cat Scool for example, are all schemes that are found from dead witchers, who where in certain regions somewhen more or less far away in the past...
Only because the Viper School has been practically destroyed by Nilfgaard, doesn't mean that Viper School Witchers coulldn't have done anything in the past in the Northern Kingdoms, while the School was still actively functionizing, so that now, months/years/decades later after htta Geralt could find in some hidden ruins/caves/dungeons/ tressure chests underwater or wheever some viper school schemes of a Viper School Witcher who was in the past travelign around the northern kingdoms for whatever reason he might have had for that...
You guys make it yourself too easy by just saying that because the school is destroyed in the present, that it isn't plausible for Geralt to find any viper gear, when there could easily have been traveling viper witchers in the past in the northern kinhdoms to do contracts there, or doing something else there, ending up having bad luck like those other witchers of the other schools and die, and either someone finds their dead corpses and thinks theres no problem from stealing from a dead witcher, like one other idiot from that other witcher schools bandits did by stealing the potions, drinking one and dieing stupidly self due to not knowing, that witcher potions are deadly for normal humen ....
I for myself would love to see Viper Gear and Sword upgrade Schemes for the two viper swords to be implemented via for example patch 1.08 to make the content of the game more complete and congruent