You put the proper words in my mouth lol. As far as accuracy, if you were saying in #29 to expect upwards of 0.5% that's more than fine. If that isn't what you were getting at, I need an explanation like I'm 5.
As far as periodic calibration of the device, it would likely be done every time it gets used. The end users can be trained on how to do this. My concern really lies in verification of the known resistors being used.