BUR #58906 has been approved by @evazion.
create alias self-propelled_anti-aircraft_gun -> self-propelled_anti-aircraft_weapon
Duplicate tag from a same class of military vehicle. Wikipedia redirects SPAAG to the first option.
I'd prefer that way since its main armament is not always a HMG or an autocannon, some are surface-to-air missiles. Post count isn't enough for implication as of today.