The functions to add / edit / delete server IP adresses have been added in the svn stable branch. I've added the chnaged files.
You can get the SVN stable release with:
svn export svn://svn.ispconfig.org/ispconfig3/branches/ispconfig-3.0.4
the required files are:
Copy these files into your ispconfig installation, then enable the new functions in the remote user. The function names are:
server_ip_get, server_ip_update and server_ip_delete