What is a good substitution for the bacon?

You could try a few dashes of Worcestershire sauce. Or a few shakes of nutritional yeast for flavor. Or some Shiitake mushrooms on the side, stems removed and an "x" cut into the caps to allow even cooking, then roast on an oiled sheet pan (brush with a little extra oil, sprinkle with ground pepper and a few drops of tamari). Or, just leave it out; the recipe sounds flavorful enough without the bacon.