Another combination I like which can make quite a good base for the sorts of meals where you want a mince type effect is finely chopped/grated onion, carrot, celery, mushrooms, peppers - with some lentils too that can be particularly nice, the puy lentils add some firmer texture to that mix, I also like red lentils, big green lentils, and am a bit of a fan of split yellow peas which are great for both taste and texture in a home-made mince substitute. Use a good veggie stock and a good glug of Henderson's (or your veggie umami condiment of choice - mushroom ketchup, soy sauce etc), a good wadge of tomato puree too if it is for spag bol or veggie chilli.
I've done some fairly epic veggie chillies using that as a base with a couple of tins of beans (pinto/butter/kidney etc. - I like 2 different types in a veggie/bean chilli)