Sorry, last one.
Pre-made meals can be easily bulked out with veg (fresh can too but more work and more visible).
So for a lasagna meat sauce, I start with my loads of onions and garlic - but I use the food processor to chop as I will have lots to chop so its worth the washup.
Mince beef is the main meat, but I also whizz up a couple of packs of Lidl's bacon lardons for flavour.
Veg includes a few carrots, a courgette, a red pepper, a large handful of mushrooms etc - all whizzed up so very fine - no one notices but they add a lot of flavour and goodness as well as bulk!
A glug of red wine, along with my tomatoes (I usually add some passata and some tomato puree so its not too liquidy for lasagna, but less puree and possibly more wine/stock if intended for a spag bol), herbs, and let it simmer for a while.
I do the same idea with shepherd's pie - carrots, mushrooms, courgette etc whizzed up in the fried onion/garlic/meat mix, but I also add frozen peas (left whole) to that.
Veggie chilli and veggie curries are great and veg is better in big chunks in those.
I also like to do roasted Mediterranean veggies a lot - all veg diced to the same size, seasoned well with dried herbs, salt/pepper, olive oil (and a dash of balsamic vinegar) - they can be frozen before or after cooking, served as a side dish to a roast, used as the base with a bottle of passata for chicken or lamb to be laid on top and roasted, made into a ratatouille, or defrosted leftovers work really well in a tomato sauce with pasta (and maybe some bacon lardons, chopped sausages or chopped chicken if meat is needed). And while chopping can take a while when doing enough for a lot of people, it's not that long and can be done a couple of days ahead (store in a large Ziploc bag in the fridge) or weeks (Ziploc in freezer) - so I find it handy to chop while waiting for something else to cook on a quieter day.