Nice! If I'd be looking into running FreeBSD it would be because I heard about its supposed security and I/O performance characteristics. Do those qualities hold up when run on firecracker this way? What applications would you choose FreeBSD for?
The biggest strength is the ports / package manager works better than anything I have tried on linux and it sticks to unix principles closer than linux.
The biggest weakness for freebsd is docker and mono support is very poor. There is a desktop distro but in general any gui stuff linux beats freebsd hands down I only use freebsd for server stuff.
I use it for production web servers, backup / storage servers, routers, virtualisation servers. I find its rock solid and more consistent than linux.