I don't really know you, so I'm just giving my opinion as it would apply to the general public.
We have digestive systems that each of us has contributed in making the way it is. And that it will change and adapt depending on what we eat over the course of weeks. Sort of like the way our bodies start adapting to yoga if we do daily yoga.
Presently, I'm in southern arizona and twice a week I visit a raw foods retreat for lunch (called the Tree of Life). The people that stay there, work there, and go there for treatments, all seem to have no troubles that you mention, even though they eat raw recipes 3 times a day. I suspect it is similar to the adult diabetes and other reasons people go there, that after a week of the retreats raw recipes that everyone starts getting better.
I'm speaking about the general public and this topic, not you specifically, maybe you are some rare 1 percent of the population that can't find a way to eat what you call a sattvic diet. But I doubt it.
I've had over 150 different vegan foods (grains, seeds, nuts, fruits, and vegetables) in the past years, so there are plenty to choose from, and many different ways to prepare them. Some are low glycemic, some are high glycemic, some are fat rich party foods, some low fat fruitarians, etc. One learns what works for themselves and what doesn't.
Also, our diet from the previous month is what decides what type of probiotics, bacteria, and enzymes our stomachs develop. And there is also the problem how much bread, sausage and eggs is in the stomach when the veggies arrive there, lets not blame gas on a fruit dessert fermenting if the previous slow digesting food is blocking its path. Smoothies in the morning are not known for creating gas, they normally digest quickly.
In short, I doubt if you would have these problems if you went to a retreat like Gabriel Cousens 'Tree of Life' for a few weeks. They know food and digestive systems better than anyone.
But who knows for sure? You and I can only guess if we don't go there and try.
Personally, I get gas from glutens. I don't know why. Bread doesn't give me other gluten problems, just gas. So I avoid the gluten grains unless I'm sprouting them first to deal with the phytic acids and enzyme inhibitors.
P.S. Lets be honest, eating is a treat and a luxury that many in this world don't get to play with much.
Today, I have an inch of vanilla bean and a piece of ginger soaking in a liter of water to flavor it. I shouldn't of bought the processed vegan marshmellows for lunch today.
Best wishes, and by the way, I'm not criticizing vegetarians for not being vegan. I'm just under the impression that this thread's topic is 'can someone be sattvic (or vegan)'. I'm simply saying that its possible to be vegan, not easy, but there are usually ways to be learned.