Why is the Quality Manager the approver? If all you’re going by is visual approval, the customer would have to approve every job. Remeber, color is a relative sensation. (relative to the observer)
The right way to get an approval is to determine your target standard (TR001 is the only likely choice at this point, unless you’re separating in house, and separating to some other standard) then print to those solid ink density and dot gain specs. When your sheet meets those specifications, your sheet is measureable and repeatable.
So you’re giving your vendors a proof. The fact that it’s printed on your DI press means little more than you’ve made a very expenisve proof! Your proofing system should be replicating your press output, that’s what a proof is for!
If the idea is to push for quality, then give them specifications to print to. Specify the important things like paper color, ink color (in Lab* at density), Solid ink densities, dot gains, etc… Giving them a sheet from a press (or even a proof) means nothing if they don’t know how that sheet (prrof) was created.
Here’s the beauty of this system. Make one file and send it to any printer in the world that’s capable of and advertisies they print to SWOP (TR001). When you get the product back, it will match! If it doesn’t, you can tell them exactly why. (Because you know what to expect and can measure it)
There’s nothing wrong with supplying a proof to your vendors, just make sure it’s printed to a specification and that specification can be met and repeated. (for instance, don’t run Magenta at 1.8 because you want more “punch” in the red… that’s out of spec and some inks may not get to 1.8 without a TON of gain)