Hubris, good enough, and Lamarck
When I hear people say that genetic engineering goes against nature, I say that's a good thing. "Nature" is a mindless goalless process, so if something is against nature, then it must be intelligent and driven by a purpose.
The gears of natural evolution grind ever so slowly, but the nature of the system guarantees a correct answer eventually. The rules embody the concept that "the enemy of good is better", and stops at good enough. Natural evolution won't produce the best answer, just a workable one.
It's very human to not want to wait an evolutionary epoch to see results, because our lives are so much shorter. But you open yourself to the charge of hubris, even of "playing God", if you presume to be able to make all the decisions correctly to build a new organism in one shot. Nature had the luxury of trying millions of different things until it found one that worked. Nature gets to bury its mistakes and move on, but you'll have to live with yours.
Don't forget that natural evolution created the human brain. It's only "good enough", so be careful of thinking that it's capable of achieving a perfection that Nature cannot.
Lamarck is an interesting case these days. He was just wrong fundamentally, but now it appears that there might be circumstances in which significant change can happen in as little as one generation. Sexual selection can produce very rapid results. If all the females (or in fewer cases, the males) of a species simultaneously decide to choose mates based on presence or absence of a given trait, that trait will dominate (or be suppressed) in one generation. It will look like Lamarckian inheritance, even though it's true evolution in action.
Dawkins posits that a couple of million years ago protohuman females took it into their heads to value male traits dependent in various ways on bigger brains. Maybe better coordination leading to graceful movement. An ability to make pleasing sounds that eventually became song and speech. Skill at crafting useful tools for the home cave. An ability to work out how to preserve and safely apply found fire. And of course hunting skill to bring home the bacon. In the blink of an eye in evolutionary terms, our brains doubled in size.
Yet another reminder of how much we owe our womenfolk, isn't it?
However, you're proposing strong Lamarckian inheritance, and it's telling that your description is vague. You need to be more specific than "A type of biofeedback mechanism" or "redirected for other uses" (by what mechanism?). "cause a species to modify its DNA to adapt" is suspect because there's a hint of intention there--a species has some unspecified means to modify its own DNA if external pressures "convince it" to do so. You're positing something beyond simple reproductive selection by external forces.
You have a long way to go before you can rehabilitate Lamarck.