I appreciate the thoughtfulness with which you present your view, and also see it's validity-- that one purpose of prison is for the government to take a measured and limited 'revenge' for the victims of harm. Where the alternative is blood feuds.
Thus prison should not be comfortable, for those rightfully convicted of crimes involving harm TO OTHERS.
But by this same line, that the government's actions should be measured and limited. Prison should not be cruel, nor should the punishments be unusual.