You guys might try Brown Rice Syrup instead of Dry Malt Extract. It has about the same fermentability, but has very little taste. This should let your tea taste shine through. Make sure to add some yeast nutrient as well if you only use BRS.
We have done GF tea beer over in the gluten free forum for those who are interested. Sounds somewhat similar to the main purpose in this thread, and also when someone asked about adding black tea to beer.