Something based on
Code:
raw 473:*:{ msg chanserv invite $2 }
You may add checks like "if (r isincs $usermode)" etc.

Now a CS invite will only work if you've identified for that nick, which may take a second or two even if you use some auto-identify script (again no in-build feature). If you consider timers as workaround, please read this thread. A better choice could be the /autojoin -dN command.