I came up with this new mechanic and wanted to see what people thought. The only use I've considered it for so far is when characters spend a lot of time crafting and get tired/inattentive.
UPGRADE/DOWNGRADE A ROLL
An upgraded or downgraded roll has it's open-ended numbers modified. An upgrade is an improvement, decreasing both the low and high open-ended chance by the number of upgrades applied. A downgrade is a penalty, increasing both the low and high open-ended chance by the number of downgrades applied. For example, a roll that is upgraded twice puts the low OE at 01-03 and the high OE at 94-00. Conversely, a roll that is downgraded twice puts the low OE at 01-07 and the high OE at 98-00.