Parzival, I've been thinking about your question about what the two "liquids" are and "coming up with something new." Waite does reveal a lot in his usual backward way.
First, "It has one foot upon the earth and one upon waters, thus illustrating the nature of the essences." Then, "It is called Temperance fantastically, because, when the rule of it obtains in our consciousness, it tempers, combines and harmonises the psychic and material natures." One essence is psychic, the other material. They look like liquids, but they're energies.
The angel represents the enlightened mind. Waite again, "It is, moreover, untrue to say that the figure symbolizes the genius of the sun, though it is the analogy of solar light, realized in the third part of our human triplicity." It's that third part that balances the other two.
What it all seems to point to is summed up by, "it is the analogy of solar light, realized in the third part of our human triplicity." It's an illustration of the emotional (what Waite calls psychic) and material energies brought into harmony and balance through the influence of an enlightened mind. These core ideas could be expanded in a number of different directions, but this gives you some idea of what Waite was trying to say.
I'm not sure this is an illustration of anything new being created. I believe Waite dismisses that notion with his comment, "All the conventional emblems are renounced herein. So also are the conventional meanings, which refer to changes in the seasons, perpetual movement of life and even the combination of ideas." It seems to more precisely reveal a principle, that of the influence of the enlightened mind and its role in an individual's progress.