Unfortunately not. Sysbox requires "true root" privileges, so it can't run inside a system container deployed by Sysbox itself (since that system container would use the user namespace). You can run Sysbox inside a privileged container however, and in fact the Sysbox test framework relies on this heavily.
What use case do you envision for running sysbox in sysbox?
What use case do you envision for running sysbox in sysbox?