???? I use bulk migration with live migration and it works well
so as a result Bulk Migration doesn't work with LXC? (yes)LXC will be migrated in stop mode of course (no live migration for lxc)
I don't know what your problem is, I don bulk migrates for maintenance, the VM's do live, the LXC containers do stop migration as they should. I never configured something specially regarding this.
I don't have such a large number of containers. Maybe you can script it? proxmox has a nice API