That's brilliant, thanks! Does this account for automatically calculating the product cost (without privileging the main product from the by)? Or is it just for inventory but not for cost?

Unbuild orders would also be cool but they need to be built first, since it's asking me to reference a BoM - not sure if this is doable.

Unless maybe I can use the "Kit" kind of BoM to do that... I'm investigating.

With a Kit BoM you could just Purchase the "parent" product, and on your WH/IN receipt, this would be split up into the containing products already.

Yeah Kit seems to work amazingly, thanks a lot!!!

WARNING for any future reader: do NOT use Kits! They are a flimsy feature not designed for this sort of use, and they will completely mess up your database. Kits are for products that you order separately and sell as a Kit. My use case is kind of the opposite: I order the Box, and I may either sell the full box or its single components. This does not work: https://www.odoo.com/forum/help-1/a-product-with-a-kit-type-bill-of-materials-can-not-have-a-reordering-rule-280844