If Heiskanen falls to our pick at 5 and Vilardi and Glass are off the board I could definitely see Benning considering him. A Juolevi-Heiskanen would be our top everything unit for the next decade+. That unit would have excellent shutdown, puck moving, and offensive ability.
That said, I don't know how the fan base would react picking a defenseman at 5 two years in a row when there are some high ceiling offensive prospects on the board like Pettersson, Mittelstadt, Necas, and Tippett.
If Heiskanen were to be available at 5 I think the right move for Benning would be to trade picks with Buffalo who holds the 8th pick and get another asset. Buffalo is in need of defensemen and if they can get LHD Heiskanen they could pair him with RHD Ristolainen who is Finnish as well. That would allow us to pick up an extra pick or prospect while still staying in a position to draft one of Pettersson, Mittelstadt, or Necas.