Going to go off the range here, admit my ignorance, and attempt to make sense of this answer that my Neurologist tried to explain to me. (Yep. I discussed this with him, for reasons.)
Basically, there seem to be a couple (or more) of "classes" of auto-generated instincts; think of them as the "firmware" that operate the biology of the creature being studied. Humans actually have more, but during their development they become sub-classed in
- "pre-disposition", such as handed-ness (right-handed, left-handed, or ambidextrous),
- "autonomous-seeming reflexes" (squeamishness, attraction to or repulsion from various environmental attributes such as dirt, dust, muck, water, etc.) that can be "paved over" with new(er) conditioning, and
- "permanent response" like pain, hunger, panic, etc. These are almost impossible to re-train, so they are considered, well, permanent because they appear to promote the survival of the being.
This is vastly over-simplified, but I think you can follow what I'm saying. What he pointed out is that we're not really sure how this "pre-programming" takes place: if it occurs, it expresses itself in the next generation of the creature (or person). A favorite example of this is musicianship, which is said to be perfected (or be close to it) every three generations. It has to do with the level of commitment of the person (or people) expressing that skill, act, or behavior and whether or not it is present (or expressed) by the male partner, female partner, or both at the time of conception. Being an Engineer of various sorts (Computer, Electrical) I think I understand what he was trying to say.
The "RNA Transfer" - at least according to my Neurologist - seems more like you want to inject perhaps a skill or ability like a drug. His take on it would be like, "Oh, you want to be Right-Handed? Well, here..." and the specialist, hack, or general practitioner simply injects you with a substance (description can be anything) then tells you that your new capacity will develop in the next week or so, "...so don't fight it. If you feel the need to pick things up with your right hand, so much the better..." He was intrigued with the idea because it would enable someone to change whether they were foolhardy, or alter their stress level (likeliness to panic, coolness under fire), or perhaps cure a person's fear of loud noises.
His final attempt at explanation was that it would be like allowing a character to rearrange their attribute scores, advantages and disadvantages (like in the Hero Game System, or perhaps the GURPS System - and countless others) long after the character has been generated, during the campaign's continued progress. He also mentioned that it's not out of the realm of reality - we just don't know yet.
So - finally - in answer to your question - it appears that there might be some traction there but it would edit the underlying fundamentals of a person's general makeup. We're not too sure if you couldn't also expand an individual's capacity to learn (raise their IQ maybe?) through this same method. You are, after all, re-writing some of the most important building blocks of the individual. Maybe enhance their body's capacity to process neural signals (maybe through expanded nerve pathways?) increasing and individual's basic speed (running, or drawing a firearm from a holster) or increase their sensitivity to touch (like sensing textures, reading braille in microfine points).
According to my neurologist, this would be like the basics for creating mutants (like the X-Men) because depending on the details those changes could naturally express in the next generation: the subject's children. And if both partners had been thusly modified, the end result could be anything from a preternaturally fast human with mesomorphic skeletal construction and unbelievably fast healing or a hopelessly myopic person with reduced hearing and hemophilia --- or some other unexpected foundational shift, for good or ill. As Batty Coda said in Ferngully: "It's Darwin's grab-bag!"