MAAS currently only supports Ubuntu version 12.04 to be installed on the nodes.

When adding support for other releases, it might be important to consider that pxelinux.0, chain.c32 and ifcpu64.c32 are being copied from the syslinux-common package installed on the host system. However, if I look at the md5sum just for pxelinux.0 over time, it seems to have changed for each release:

  86d7c19925f7cb5d9f1f54c0dec7812a 10.04
  0ae389801f547ccf19bd6f63c0ab3b7d 11.04
  a13943e52958d1789bc326a7a3917959 11.10
  94fa5add303db869b79cba07449127c2 12.04
  4fa6c990876212a5d94ba64dca618a21 12.10

So, it might not be possible to always use pxelinux.0, chain.c32 and ifcpu64.c32 from the host for deploying older and newer releases. This change would also imply that the target directory where the files are copied would have to be specific to the release. For example, the pxelinux.0 file is currently being copied directly into /var/lib/tftpboot whereas it might have to be relocated to /var/lib/tftpboot/$release. This change would in turn imply that the dhcp configuration, whether it be in dhcpd or dnsmasq, would need to point to the appropriate target depending on the release intended to be installed on a target system.

I'm not sure it matters what syslinux binaries are uses, they are pretty release agnostic. Testing will help :)

If it doesn't matter, why does someone bother to change those files every release? Also, the assumptions made for an LTS might not hold true until the next LTS. For example, Lucid didn't need chain.c32 to netinstall some systems but it was needed from Maverick onward. This example is simply intended to sound an alarm about using files from an LTS release to commission future releases.