However, once in the landing config, and with the appropriate VAPP inserted into the MCDU, why can't we use managed speed to take advantage of ground speed mini protection?
You won`t have VLS though - if its a double SFCC failure.
As PENKO said
So do not just start retracting flaps or slats, mind the speed limits!
Take it all one step at a time. Read your QRH.