It's not a gap, it's an absence, and the deficiencies incurred by eating zero fruits and vegetables are not analogous to a b-12 deficiency (which most meat eaters also suffer, just to a lesser extent than vegans). These deficiencies aren't going to be made up for in pill form. Not to mention consuming no fruits and vegetables means you are essentially on a very low fiber diet, which has huge health implications on its own and is probably a bad idea.

This is a lot of work to go to in order to hang on to a pet diet that is shown to cause arterial injury and doesn't lead to greater weight loss than less harmful diets.