As a veteran of the McDougall Maximum Weight Loss Plan back in 1996, I feel pretty well qualifed to answer your question.
Dr. McDougall has actually had pre-packaged foods for some years now. (they're marked as "Smart Foods"). For the most part (from what I've seen) they are the cups of dehydrated soups that you pour boiling water in and let sit for five minutes (I remember he had soups, hot cereals, mashed potatoes, etc.). I still see them in the stores around here - in the soup and/or cereal sections mostly.
The ones I've tried ranged from bland to nearly inedible...
I was not a repeat buyer of them.
As far as his diet is concerned...unless he's changed it, it's a pretty drastic ultra-low fat, vegan plan...here's what you CAN'T eat on it:
1) No fats or oils of any kind
2) No animal products of ANY kind
3) No soy products, including tofu of ANY kind
4) No flour products (i.e. bread, tortillas, etc.) of ANY kind
Here's what you can have:
1) Fruit (limited to one a day)
2) Veggies - unlimited
3) Starches and grains such as potatoes, brown rice, quinoa, etc.
4) Decaffinated herbal teas and water
5) Sugar in moderation (i.e. on your oatmeal)
Needless to say I lost weight...I also lost some of my hair...and my skin was so dry and itchy all the time...and of course as soon as I started eating 'normally' again...I started regaining the weight very quickly.
Incidentally, I followed the McDougall plan in conjunction with a hypnosis center - this was the diet they advocated. Keep in mind that this was in 1996, when everyone was convinced that fat was evil and that the less fat you ate the better. I think my fat consumption got down to 5% of calories during that time!
Once I started eating animal products again...and added healthy fats to my diet - my hair and skin became MUCH healthier.
Just my two cents...