I'd like to say DIY ovens are hard; don't even attempt it :) but if you are interested in really good pizza, pita, bagels, and ciabatta all you need is a conventional oven modded basically like this[0]. Also a baking stone is required. SV takes too long, is it worth it?
Try 1/2 inch sheet steel instead of a baking stone. More thermal mass, better conduction and more wear-resistant (won't crack from thermal stress). Cast iron is a cheaper alternative.
Sous-vide won't work for breads. The best bread is going to come from an oven that's using heavy convection current to crisp up the outside. A brick oven does this, as do the more modern convection units.
If you want to see what's new in convection cooking, check out the Turbo Chef Fire. This is a commercial piece of equipment, but could eventually be adapted for home use:
[0] http://www.instructables.com/id/Hack-a-Toaster-Oven-for-Refl...