For me the missing bit in Fly is scheduled tasks. I know how to solve this by spinning up an app that runs permanently as a scheduler, but basic cron-like scheduling should be part of the platform IMO. All other FaaS-like service do this.
I'd love to do this, if for no other reason than I hate working with cron. What would you use it for? What would the ideal version of this feature look like for you? What kind of apps would you be more easily able to ship? Is it mostly so you wouldn't need to keep a single tiny running VM sitting around running cron?