You could put electric strip heat in the ducts but you would have to add in the electrical cost of running the fan. They work like toasters.
Electric heat is 100% efficient. Only trouble with that is it's cost.
Find out in your area what fuels are available that might be cheaper. Forget oil.
If that's not doable you could change out the a/c units for heat pumps and that might be the cheaper. Heat and cool with the same units.
I should have played the g'tar on the MTV. MK
You can be anything you want......As long as you don't suck at it.