I don't think there is a correct answer here, personally I think a Channeler is born with a set of OP abilities born into them ... Strength in the Power, Flow Affinity and whatever Talents may surface. This is no different to me than Brown eyes, or red hair or how tall a person may be... Those inborn traits make a person more likely to pursue certain professions, much like a very tall man might become a basketball player or a woman with a particularly strong Healing Talent (Nynaeve) ends up a Wisdom of her village. Certainly there are short men who pursue basketball and women who have the desire to Heal despite a weak Talent, but they face a much harder road to success and may end up side tracked (Egwene) by other more natural pursuits (Traveling or Cuendillar) or like Elayne (who also showed early interest in Healing) end up studying Ter'angreal. You'll note they both moved down paths of discovery only after they discovered particular strength in these areas.

I don't see predestination or "magic" here I see genetic markers that make an individual more likely to succeed at certain tasks. Nothing says they MUST become Yellow Ajah simply because they are strong a Healers ... Moiraine ignored it despite strong Talent and at least a little desire to Heal. Her non-Channeling aptitude proved stronger in her and thus she pursued the Blue way of life.

All of what you say bears merit, no question about it, I just don't see it as the type of ability that can so easily be trained in the way you describe. And it doesn't explain Talents like Foretelling, Dreaming or sensing ta'veren ... These all seem to be Talents you either possess or do not.

With that said, necessity is the mother of invention ... How one uses their gifts is a whole other question. Perhaps a woman who doesn't have the "traditional" Healing Talent discovered the Heal-all weave in the AoL and was able to pursue her dream... Androl is certainly making the most of his one strong ability and uses it in innovative ways.

I actually saw a very interesting study on identical twins and how even when they have wildly different (separated at birth) backgrounds still end up being remarkably similar ... Some crazy stats about how many of them end up in the same career or married to the same type of personalities etc ... Our genetics guide us much more than people like to believe.