I am working on https://github.com/isola-run/isola which uses gVisor (not firecracker) on k8s (or something like kind, locally). Includes snapshotting, network controls and everything. Hope you could find this useful
I'm using https://coder.com for all my development containers. I've got mine hooked up to a k8s cluster, but anything that you can provision with Terraform can be used (e.g. docker containers).
firecraker is optimized for lambda. ie: fire and forget. not so much live systems that maintain long running state. also, I dont' think you can run it on top of a hypervisor.
A friend already made something similar for personal use, but using docker containers hardened with gVisor.