Kubernetes v1.19 will become GA soon with support of cgroups v2. Now FCOS disabled cgroups v2 with cmdline but will you make cgroups v2 default immediately after kubernetes v1.19 release? (Or make this an ignition option?)
There is currently a discussion about this topic in the fedora-coreos-tracker. I think the current plan is to make it easy to set cgroups v2 via Ignition.