There are existing group tags in a couple of fandoms I know of; I actually used them in my nominations. "Blood Blockade Battlefront" has "Libra and Leonardo Watch" (Libra being the organization the protagonists work for in canon), and "Fullmetal Alchemist" has "Roy Mustang and Team Mustang" (even though Mustang's subordinate officers are absolutely never referred to as anything like that in canon). Since these are just outgrowths of usage within the fandoms, though, I suppose they wouldn't really apply to anything worked out specifically for this exchange.