I would like to see a Wake-on-LAN diagnostic tool built into the Firebox. This would allow an admin connected to the firewall to remotely wake a device on the LAN when no other device is available to remote into onsite.
Or a packet filter that will pass WOL packets over an SSLVPN. That would work for me.
I've opened up a bug report/enhancement years ago, there is currently no Wake On Lan support at all through the Firebox itself. Hopefully it gets added in the future, but it doesn't seem like its a high demand feature.