Again, this is useless information. All herbivores eat throughout much of the day, it doesn't make raw plant food less useful for them, it's just a matter of calories/nutrients. I strongly suspect that if chimpanzees suddenly turned to a diet consisting mostly of meat that they would start suffering, healthwise.
Another completely irrelevant straw man. Neither Harris, nor Lonsdorf nor Wrangham argued that plant food is not useful for chimpanzees or that they should eat a mostly meat diet.
I'm not against anyone eating any plant foods, so I'm not arguing that (nor do Harris or Lonsdorf argue this, and Wrangham argues nearly the opposite). That's one reason I often call myself a carnivore rather than a ZCer--facultative carnivores like wolves eat some carb-containing plant foods, such as berries, as you yourself have pointed out (and even liver contains some carbs)--even though I'm essentially ZC at present. It's more of a mouthful, but maybe I should use the term "facultative" more often in describing myself, to reduce confusion and straw men. To this end I added "facultative" to my profile.
Again, I'm not remotely convinced of the above argument re "frankenfoods". As cherimoya_kid pointed out, most fruits nowadays(and even meats) have actually a very low level of nutrients than found in the past, due to intensive farming methods. In other words, even the artificially-created fruits would be perfectly fine if grown in good soil etc. And those "frankenfoods" aren't really comparable to genetically-modified fruits with fish-genes in tomatoes, the latter being more correctly labelled "frankenfoods".
My understanding of Harris' use of the term "frankenfoods" was a broader one applying to any change in a food that resulted in a deleterious effect on the diet. In this case, [domesticating] bananas to make them edible, with less seeds and more fructose (and my guess would be less bitterness also). The decreasing levels of nutrients and increasing levels of sugars in plant foods because of thousands of years of hybridization and the declining quality of soils you mentioned are additional good reasons to not rely solely on commercial plant foods, which make up the bulk of the world's plant foods, for nutrition. The genetic modification you mentioned is yet another reason to limit them. Other reasons include pesticides, herbicides, chemical washing, picking too early, ripening artificially, etc. These multiple deleterious changes, including more than just poor soils, don't somehow cancel each other out. On the contrary, they reinforce and make the case even stronger for not relying too much on commercial plant foods like some raw vegans and vegetarians do.
It think we can at least agree that Cavendish bananas, which dominate commercial export markets and US supermarkets, are not recommended. The demise of the Cavendish is expected to occur "within the next 10-20 years" anyway ("Bananas Are Dying, Killed by Corporate Monoculture," Heidi Stevenson, 2 June 2008,
http://www.naturalnews.com/023339_banana_bananas_disease.html), and all the other species of banana will not be able to fill the void for a long while, unless someone develops another commercial cultivar in the meantime.