Does anyone know of any good orchestrators for Firecracker VMs? While the technology is great, the CLI and API are still a bit too complex and low-level to implement some basic use cases in production.

Take a look at Weaveworks Ignite for an open source tool for running Firecracker VMs from container images: https://github.com/weaveworks/ignite

And of course AWS Fargate and Lambda use this tech under the hood transparently, so that's always an option if you don't want to host and operate it yourself.