I have a product that I bought a while ago but did not try so I am not sure exactly how well it works but it is basically a gluten free gluten additive for gluten-free Flours.
It is from Orgran and the product is actualyl caleld Gluten Free Gluten now that I am looking at the package. Supposedly it gives gluten-free flours "workability and versatility"
From the packaging - Thsi product will provide structure and will mimic the physical protein found in wheat in a way that will allow you to make a dough or batter with similarities and consistencies to wheat based ingredients.
Hope that helps.