It would. I use fish shell here, yet I prefer writing my build tasks with plain JavaScript. Fly seems to be a thin abstraction to accomplish the same. Now, the most striking advantage is support for generators/co-routine style for async stuff and also promises right from the get go.
I guess it depends a lot on your infra, but wouldn't (ba)sh be the most universal shell? so if shell = bash, then "shell script" = "bash script"