This solves the rogue operator problem, but doesn't solve the bit where an operator comes in expecting to build a large mining installation. Even if they paid something close to the export premium (perhaps lower due to diminished transmission losses), the asks are larger than the utility currently provides.
This leaves the utility with a dilemma. Bitcoin miners can up and move pretty easily, but the hydro dams are stuck for life. If somewhere cheaper pops up, or if a double spend attack causes a bitocalpyse, the utility has little recourse but to pass on the costs to remaining consumers.
That way the average person on the street doesn't lose, yet the miners are encouraged to get lost.