A very simple solution. For the most part, keep tempering exactly as is. However, when you have finished all your tempering attempts - you are allowed to make Just One assigned affix from only one temper - BUT it will always roll the Lowest Value.
Its simple. you will avoid bricking the gear completely. But it allows for being lucky if your first few rolls rolled with higher values. But you are only allowed to Assign one temper value and not both tempers, so you still need to be careful which temper rolls you want to use them on. And limit this only to ancestral items - since they are going to be so rare going forward.