Thank you @mauricetoet, yes, I feel the same way. Using the l-calibrated image viewer option immediately tells you if calibration is working correctly. I always check it before I continue to star analysis.
On the other hand, while creating the master frames, it will be most helpfull to give warnings to the user if they follow a calibration workflow in which the bias correction is not done properly for both light and flat frames. I really feel the bias pedestal is the root cause of most calibration issues, especially proper flat-field correction. So like @keesscherer recommended, I will try to create a warning system in the calibration engine which could be shut of as well.