GUI addition suggestion: interface-mtu
Given the lack of a specified maximum packet size for Gbit ethernet, I would think that bringing the "interface-mtu" option to a box on the DHCPD GUI would make sense. This came to my awareness through wanting to cut down the MTU so that I can run VLANs through unmanaged switches. This would avoid having to manually configure every client, which is particularly impractical with clients not under your administrative control.
There would be room for subnet, subnet mask, and subnet mtu all on one line. Blank would leave interface-mtu out of dhcpd.conf .
My understanding is that 2.0 will enable specification of arbitrary options as numbers (somehow), so it could also be done that way. Please let me know if I misunderstand.
You can set any option you want in 2.0 via the numbered options, so this is already solved there. There won't be any more updates to the 1.2.x line so if you want that option, you can either upgrade to 2.0 (not recommended for production environments yet) or or look at the relevant code in 2.0 and try to backport it to 1.2.x (might be feasible if you're familiar with PHP).