I think you could argue that the whole swarm was ectoplasmic while your body was off in the Nevernever, that'd probably easier than turning the whole 300lb physical mass into separate creatures. I think. Who knows, it's magic
As long as there is some sort of working explanation I think it works
Plus if people can become swarms then a Were-Hornet becomes viable! Imagine that as an NPC in a campaign, even just as a sideline monster that can be vanquished without feeling guility. I mean, who likes hornets?