Gas oven heated from the bottom
There isn't anything wrong with ovens heated from the bottom, many actually are. It's actually better that way because heat rises, if the element is on the top you'll get an oven that is hotter at the top than the bottom. 

With a baking stone the principle is the same no matter where the heat comes from, with the same benefits, just make sure that there's space for air circulation around the stone. Also, baking stones take time to heat up, so leave more time for preheating.