[Feature Request] Allow defining hostnames only in DHCP Reservations

Currently DHCP Reservations require an IP address. Would it be possible to allow reservations that are hostname/DNS only?

I have a number of devices that I don't care what their IP is as long as I can assign a hostname since the device doesn't report it's own name. Having the option to create hostname only reservations would allow me to set these up and no matter what network they connect to the hostname would follow.