Since you have to, at some point, trust the manufacturer that they built what they said they built, there is no point in a "trustless" system. Second, you have

Since you have to, at some point, trust the manufacturer that they built what they said they built, there is no point in a "trustless" system. Second, you have yet to actually provide any motivation for end clients to spend money or hardware on a manufacturer's blockchain. Chances are the manufacturer would have to maintain all the miners, which is silly. Third, the manufacturer in this case would have all of the signing keys, since they're the only ones that can make parts. This also damages the selling point of the blockchain. So no, this does not work.