Fully submerged water bath for stove top baking?
Unlikely. Without even getting into the mechanics of how it would work, simple physics dictates that you can't get the temperature of this "immersion oven" above 100 degrees Celsius. Most cakes and breads are cooked at temperatures above 170 degrees Celsius. A second issue is that moisture can escape when baking in a normal oven. Your "immersion oven" would not allow steam to escape whatever you're cooking, which would lead to the contents being a bit steamed as well as baked. Sometimes this is desirable (see eg making bread in dutch ovens), but not for the majority of breads and cakes.