Mashed potato do not fare well when frozen. They become grainy and the texture and flavor are disgusting. I echo the others regarding the topping.
I would be inclined to freeze the enchiladas separately from the sauce. I think the tortilla would not hold up to the defrosting.
The Cooperative Extension Service has some good free info. This publication is a handy starting point.
Are there still any of those businesses where you go and put together meals for your freezer using their ingredients/containers? Years ago I stole many freezer meal ideas from studying their monthly offerings. Most of their offerings boiled down to animal protein + a non-cream sauce to help keep it from drying out. Ex: chicken parmesan, veal marsala, etc.
I tend to freeze non-cream soups, stews minus potatoes, cooked meats with sauce & dumplings. For something like lasagna I make double my meat sauce and freeze it. Then most of the time/work has been done and the other ingredients/assembly are pretty quick.
I would look at a commercially frozen savory pie at the grocery. Istr the cooking directions seemed similar to those you would follow if making the item from scratch. If so, I would try freezing the hand pie uncooked. I would later cook it without defrosting.
