I see the appeal of FSS; I've felt frustrated with the extra effort it takes to describe some operations using Ansible compared to shell scripts. However, your project suggests to me that what we may really need is a tool to translate shell scripts into (reasonably idiomatic) Ansible playbooks, perhaps interactively and with further review from the user. That, or to otherwise automate the creation of playbooks where possible.

Edit: removed speculation about an idempotent *nix shell.