This sounds like a great idea, but you might want to know that a certain percentage of the population is allergic to tea tree oil, and as to those people, they might end up getting contact dermatitis or eczema from using it on their skin. That's what happened to me when I tried a new soap with tea tree oil in it. Here is an article on tea tree oil allergies:
This doesn't mean that tea tree oil causes problems for everyone, though. I just wanted to let you know to be on the look-out for it if you are planning to use it in a product.
By the way, you once said that you were considering preparing an in-between herb product. I've always been very interested in that. If I may ask, are you still considering this? An in-between herb product would be so great.