Pimox is a port of Proxmox to the Raspberry Pi allowing you to build a Proxmox cluster of Rapberry Pi’s or even a hybrid cluster of Pis and x86 hardware.
Proxmox VE is the thrifty persons VMWare ESXi or an ops-limited persons OpenStack. I’ve definitely enjoyed it at work for managing VMs on just a single node. There’s a stack of RPi 3s on my desk where pimox would be applicable.
Pimox installation doesn’t look to be easy peasy, but at least a manageable, cuddly afternoon with the CLI.