Firecracker on Freebsd 14 EC2 instance / or is it possible to build and install new kernel in AWS EC2 instances

Recently there were some work done to make Firecracker to work with Freebsd, i wanted to test that. For that as it was stated here https://www.daemonology.net/blog/2022-10-18-FreeBSD-Firecracker.html and here https://www.usenix.org/publications/loginonline/freebsd-firecracker , what i need to do is just build and install new Freebsd kernel with some specific configuration to make it work with Firecracker. And everything goes as it should, until i reboot the instance, after which i get in status 1/2 checks passed or insufficient-data, and im not able to connect to it.

Im using c5n.metal instance type.

Is it even possible to change kernel "on a fly" in AWS infrastructure? and im just missing something, or it is forbidden from the AWS backend side?