So what would be an appropriate punishment here?
That is a very good question. Whilst we all want revenge that's not what the system is primarily for.
Having said that there needs to be a deterrent. For this I think back to the bad old days of drink driving, when it was the norm to go out drink 4-5pints and drive the short way home, if you got caught you were a bit unlucky. But drunk drivers were causing accidents, of course the perception was that it wasn't your social drinker that caused this.
However with more and more draconian penalties for drink driving people stopped talking the chance.
Therefore we need a deterrent sentence for killing someone whilst in control of a car. At the moment people drive inappropriately because they know the penalties will not be too severe.
If it was the standard that if you killed someone whilst driving you were deprived of your freedom then slowly (just like drink and driving) normal people would modify their driving. Unless this happens and the driver is just thought to be unlucky for causing the crash then things will not change.