(it is possible, I imagine to use grated yellow squash (like Butternut) or rutabaga perhaps or maybe grated cauliflower (just nuke or fry briefly to soften a bit))
Variation: Using Mozzarella Cheese - I also used a bit more on top than suggested...yum! When I made them a second time, I forgot to squeeze the moisture out of the chayotes, so I let the mixture (I had mixed everything already) drip through colander briefly and then I stirred in 2 tbsp (30 mL) coconut flour to absorb excess moisture. I baked them for 30 minutes instead of 25 minutes, switched off the oven and left them in there until I was almost ready to serve dinner. I took them out 15 minutes before serving. They firm up nicely when they come to almost room temperature. They were perfect! Good save! ;) The "messed up "ones are pictured below.