I make a 100%vegetable sauce that usually gets used over pasta by adding some extra basil etc, but I make it neutral enough that it could be used as enchilada sauce, sauce over couscous with roast veg, by adding different spices.
As long as you add a couple tins tomatoes, some onions, then everything else I have varied, butternut, beetroot, lettuce, courgette, celery, carrot, peppers, garlic, mushrooms, leeks, pumpkin, spinach.
I wouldn't use brassica's in it though, might go bitter.