Lastly, when you create your Reseller, just make sure you assign them to the server IP, and it will be swapped with the shared IP for their control.
Note that "add"ing more IPs (126.96.36.199+) will always be added, based on how that's scripted, regardless if the account was created on the server IP or not. More coding would be needed if you need other scenarios.
Note that their User Level domain will still be set to the server IP. More perl regex calls would be needed to accomplish that (user.conf, user.ip_list, httpd.confm domains/domain.com.conf, domains/domain.com.ip_list, /var/named/domain.com.db)