Do you ever get Lucid Dreams where you just become lucid because you just know that you are dreaming. I get them sometimes, and I'm very sure that you would be able to refine a technique to recognise it more often. So to answer your question, yes I'm certain that you could use the "dream feeling" as an RC, however I don't think it's the most reliable of RC techniques because sometimes you wouldn't be sure. Might be best to use this as your primary method for noticing a dream, but have a back-up RC just in case you're still not sure.
As you have correctly mentioned, this could well be the reason why some people are able to LD naturally from a young age, and also it could explain why often people will go through a burst of several lucids a few nights in a row, then nothing for a few weeks, because they were more used to that "dreamy feeling" at the time.
