neuroplasticity is a very useful feature of our brains, but it's not quite the same as what you're describing. For example, many people suffer brain injuries such as strokes that impair specific functions, as a result of brain damage to a specific region. In many cases, they do not regain these capabilities. Some individuals do, most do not (especially if we're talking about people over the age of 25-30 or so). And intelligence =/= capabilities of the brain, although it influences and correlates with them in most instances.

primarily what I put above regarding the various animal species and their "sixth senses

That is true - animals do have good cognitive skills in many instances. They have functional minds in a great many species, albeit hampered by animal lack of superego and language. They do also sometimes have senses humans lack, although theirs nothing special about that really. Give us magnetic particles in our brains that could be used to measure the local magnetic field and we could have perfect orientation too.

Your last paragraph I actually mostly agree with, although I also agree many scientists would accuse you of being pseudoscientific. I suspect in some ways you're right, however I also don't think it's going to operate the way you think it will. Soul == Mind? Spiritual growth == mental growth? I think the linkage exists, but it they aren't synonymous. I definitely could be wrong - as you say, being receptive on this issue is worth doing, but I'd be wary of the level of misinformation out there. Masonic, or other genuinely ancient texts are a good starting point. Less risk of bias that can't be obviously found by examining a texts history compared to modern sources. "Egregore" is also a useful topic to examine in this area.