what exactly is so bad about standard dry dog food? I fed my previous dog the brand ProPet (Carnation owned). She never once complained about it, and 2.25 cups kept her right at 74 lbs for the better part of 10 years. If I needed for her to gain weight (e.g. for winter), then I increased it to 2.5 cups. If I wanted her to lose weight it was decreased to 2 cups. Until she got Lymphoma, people would guess my 10 yr old puppy as being 2-4 years in age. Such was her vigor and energy level.
Currently I have a 8 month, and 3 month puppies thriving on the same brand puppy formulation (32% protein/18% fat). The 3 month old mostly Black Lab is growing like a weed on it. The 8 month old (Pyrenees?/Lab/?) runs like a deer, and bounces off the wall with her energy. Yes I anticipate in a few months their days of free choice will come to a close, and I'll have to dip down from the puppy formula to the performance formula (30% protein/15% fat). But for now table scraps are something they get as a bite or two at the end of my meal, rather than a meal un to itself.
Although you bring out several good points as to what might cause GI upsets such as change of food, I perfer the alarmist approach when it comes to vomiting. An obstructed bowel can become gangrene in 3 days.