Balance is a thing you actually learned at the young stages of life. It has become natural.
If you teach balance and position at the conscious level as a must, balance and position may be perfect but the ball may hit the player on the head (a humorous idea) because his attention is on enforcing the wrong thing.
High level tennis, in my opinion, is played with the hand. As a beginner you can learn the basic stroke just standing there with someone feeding you an easy ball. Gradually the body will adjust by itself.
I know I am disagreeing with the whole field with this, but the results speak for themselves.