Ok got a little help from our apple SE on this one..
Turns out the syntax I was using to modify the /etc/bootpd.plist was wrong (not surprised). The servermgrd attempted to verify the contents of the bootpd.plist and decided they where invalid. It then renamed the file to /etc/bootpd.plist-corrupted and created a new /etc/bootpd.plist from scratch (big surprise).
Here is the code I ended up getting to work.
<key>relay_enabled</key>
<true/>
<key>relay_ip_list</key>
<array>
<string>10.0.0.2</string>
</array>
So if you are hacking up config files and the changes are flushed check for a -corrupted version of the file.