You can use TVP to add texture to the tamale in place of ground meat. There are also tamales that are made with fruits, such as raisins or dates. Do a quick Google search and you will find more recipes than you know what to do with.
When using TVP (textured vegetable protien), place it into a flavored liquid such as a veggie stock with herbs and spices. As the water reconstitutes the TVP into moist granules, it will also carry the flavors. Then make your chile or tamale sauce, add refried beans (made without lard) as a thickener, and roll your tamales. Steam them as usual. I'd be willing to bet that many who ate your tamales would think the TVP was ground beef, while you would let them know that your tamales are meat and fat free.
Seeeeeeya; Goodweed of the North