This has long been a thought of mine, surely the 'vegetable' contents of packaged dog food cannot hold too much of its original nutritional value after processing and shipping.. I am looking into writing a guide on feeding your dogs (and cats) from home, at least partially from the garden, to reduce costs and provide a much more nutritional diet for the four legged friends in your life.. after all, we care enough to establish ourselves an abundance of food, I think it only fair to look further into provisions for our canine pals! I have so far fed my dogs peas, beans, lettuce, corn and potatoes from the garden but am on the search for an larger list of possible foods for a healthy diet than that can be combined and either fed as meals or dehydrated as treats and chews.. I know most products are meat based, and this is definitely something i am contemplating due to the dogs need for meat, but the vege content is what is important at the moment..
That's a great idea to write a guide. It's not just the vegetable content of pet food that is dodgy - there are lots of sugars in it, plus they use weird byproducts from all sorts of places that can't be used for people (look on the internet for details if you want rationales in your guide). I think raw meat plus other supplemental foods is the way to go. If you want to just focus on the non-meat aspect for now, research the BARF diet, or raw food petfood, because those people have done lots of work on the right nutritional needs of animals and how to get them without using commercial petfood.
I wrote an article a couple of years ago about this... https://ezinearticles.com/?Organic-Food-For-Your-Pets&id=440900 Its not thorough but might be a good starting point.