Can acid-fast M. tubercolosis obstruct alveoli?
Mycobacteria are on the order of 2µm in length and 0.2µm in diameter.  Alveoli are on the order of 200µm in diameter.  Obstruction is possible, but M. tuberculosis grows rather slowly.  Too slowly, in fact, to avoid being engulfed by alveolar macrophages.  

Furthermore, obstruction does not sufficiently explain the predominant symptoms of tuberculosis:  bloody sputum and the tubercles themselves.