What is the circuit amperage? With a 20amp circuit you can run a 2000w 120v element. With 15amp you should drop down to 1500w 120v elements.
I don't see any reason why you cannot use Kal's basic plan with the modifications you described, activating either the two elements in the HLT or the two in the BK, but never both at the same time. Your day will be longer waiting to reach temperature, but so it goes.