I've thought about making malt vinegar before. I know you want to start with unhopped wort though. You can buy a vinegar mother online to throw in after fermentation. Just be very careful of cross contamination. After you have finished the vinegar though you can take out half or more, and put in new unhopped beer to make more vinegar.
"People should not be afraid of their governments. Governments should be afraid of their people." - V
Secondary: Shady Lord RIS, Water to Barleywine, Pumpkin wine, burnt mead
Kegged: Crappy infected mild
Bottles: Apfelwein, 999 Barleywine, Oatmeal Stout, Robust Porter, Robust smoked porter, Simcoe Smash