Cool to see this thread resurrected. Thanks for the feedback!
Tea (or Téa or Thea) is a lovely, strong, unusual-but-not-crazy name on its own. Being only three letters, you could definitely get away with a big, long, heavy middle name or two for balance's sake. Tea Francesca Louise Smith, for example, sounds pretty complete to me. My brother's name is Ian and he has two middle names and a three-syllable surname, and I remember that when he was born, a lot of people remarked, "that's a big name for a little baby!" So to me, Tea/Téa/Thea is totally workable by itself.
There's also the less phonetically intuitive Theia, which is the orginal Greek spelling of Thea. And the listing for Thea says that it can be a nickname for Anthea and Althea (and Dorothea and Theodora that others have already mentioned), but I don't know how intuitive the TAY-uh pronunciation would be from either of those.