Does anyone have any experience feeding a starter with Tapioca flour?
Sorry no experience with that. I think it is mostly carbo-hydrate so there is likely to be food value there. I'm pretty sure there would be little or no gluten so unless you are bent on going gluten free there would seem to be little point. If you are interested in gluten free, Staffo has done quite a bit in this direction so you could look up his blogs.
Good luck with your projects.
EDIT: From another site.
You can use any fermentable flour to make sourdough. Nuts and starches, like coconut, almond, tapioca starch and the like, will not ferment and can not be used for the starter but they are fine as an ingredient in the dough. If you need a grain-free starter, you can use bean flours to make your starter.