I guess I'm in the minority when I say that this scares the Hell out of me.
We've already done immeasurable damage to ourselves through GMO food - why do we think we can actually help ourselves by tinkering with people?
Just because the science of the day says it's better or it's more socially acceptable ("preventing" disease) doesn't mean it won't be later judged to be harmful.
An easy example of this: margarine. In the early 1900's when it's popularity rose, margarine was hailed as a godsend because it was cheaper, didn't use animal-based fats and had a longer shelf-life. Now we know that our grandparents were really just pumping us full of cancer and heart attack causing trans-fats.
You are absolutely right! Genetic modification of genes has massive ramifications which are from yet understanding. It will happen nonetheless, for the outright benefit of doing so for soverign nations, especially outside of NATO will inevitably choose to utilize to their advantage.
This is happening regardless if we like it or not, the question now, would be, what can and should we do to manage this?
My understanding is that GM food is actually pretty safe. Safer in some ways than non-GM, because it is disease resistant and does not require as much pesticide use.
GM therapies for people could overcome cancer and heart disease directly, to the point where trans fats are harmless. It takes an entire lifetime for trans fats to cause the kind of damage you are talking about. There are also healthier forms of margarine you can use now that we know about that, which actually will reduce your risk relative to butter / animal fat. (But it's still calories so if you eat a lot you will get fat and this will increase your risk.)
The main reason we have heart attacks and cancer to begin with is aging. Good luck curing that with natural approaches only. No matter what natural plants you eat, your body will slowly degrade. GM presents us with the amazing possibility of living hundreds of years. It's artificial, and that's a good thing. Nature is out to get us, and wants to kill us in our first century of life. That sucks!