Having 2 types of profession plans:
standard plans as in all classic MMOs for creating the gear the first time around, works like usually
backup plans to create an accurate blueprints of physical items you already own, making a backup plans would be a profession feature (perhaps new profession or just part of existing one) and it would allow you to inspect an item you already have and create it's blueprints. These blueprints would allow you to re create this exact item at a bit reduced resource cost (maybe 20% lower cost) due to having it's higher level plans.
Creating backup plans would need some investment too, so it would be like insurance, you pay in advance to create these plans, if nothing happens to your item, you wasted money but you are insured, because if you lose your item you will be able to re create it a bit cheaper later on, and you mitigate part of damage done to you.
Profession that allows to create backup plans could be called plan drawing and could be used to create plans of already existing gear, but perhaps also to create plans of already existing houses, for the same purpose (houses will be destructable I believe).
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So what do you think?