In calling someone a "meatpuppet" we are acknowledging that they are distinct individuals but we are also suggesting that someone else is "pulling his strings" which can be considered insulting.
A better term would be "posse". In real life, "posses" are groups of people who are not full time law enforcement officers who come together for one purpose, usually the hunting of a fugitive. On Wikipedia, a "posse" would be a group of people who either form "single purpose accounts" or have inactive accounts coming together for a single issue such as participating in an AFD or RFA debate. In such a debate, "posses" should be given no more weight then a single active contributor just as is true with "puppets" currently. However, we shouldn't say that "posses" are outright prohibited.
Why the change, because it would acknowledge that a given "posse" member, while initially here for one issue, might have his own reasons for creating an SPA and is not necessarily a slave to a puppetmaster. He might even discover that he likes it here and become a good contributor in his own right. I think this would better conform to the concept of "assume good faith".