I had assumed this would be the default behavior. Count this as a vote from me for this feature as well.
Also if you had a form where the various options were listed for advanced configuration of the DHCP server that would be very useful. No fancy anything really, just a warning “This is for advanced usage” and a list of option numbers with text boxes… or one big text box where you could define the ones you want like “66=192.168.1.222” etc.
Thanks