The advantage I see by the preseed way is simplicity.
Imagine every computer has a USB-Stick (inside) with
a late boot priority.
Normally the server boots from the first disc or Raid 1,
but with IPMI or vPro you can change the bootdevice
just for the next boot to the stick.
https://en.wikipedia.org/wiki/Intelligent_Platform_Management_Interface
https://en.wikipedia.org/wiki/Intel_vPro
So you get in a few minutes a fresh install of a Proxmox
server from elsewhere. Just the connection to the internet
is needed. - Nothing else.
Imagine every computer has a USB-Stick (inside) with
a late boot priority.
Normally the server boots from the first disc or Raid 1,
but with IPMI or vPro you can change the bootdevice
just for the next boot to the stick.
https://en.wikipedia.org/wiki/Intelligent_Platform_Management_Interface
https://en.wikipedia.org/wiki/Intel_vPro
So you get in a few minutes a fresh install of a Proxmox
server from elsewhere. Just the connection to the internet
is needed. - Nothing else.