One of the things I've done in the past that is quick and easy is to use grub to chainload another bootable volume. Scp an iso or other disk image over, chainload to that, run the installer inside it as though it had just been pxebooted or booted from a flash drive. If you can netinstall from there, then you're good to go with the OS of your choice.

There's lots of ways if you have access to common cloud primatives (replacement root volume, etc) and have some creativity.

I did appreciate this post though because it's for a way I haven't used before.