I have a solution.
I make a new option under "AdminCP --> vBulletin Options --> My Hack's Settings" called "URL where your web hosting manager is located". This way I'm not limiting any users....
As I was writing I thought of a problem. I only know how to write an automated script for cPanel's WebHost Manager. All I do is pass this URL
Code:
$submit_url = "http://".$vbulletin->options['whm_domain'].":2086/scripts/wwwacct?sign=&plan=undefined&domain=".$hp['subdomain']."&username=".$hp['host_username']."&password=".$hp['host_password'].""a=".$hplans['webspace']."&cgi=1&frontpage=1&maxftp=".$hplans['ftp']."&maxpop=".$hplans['email']."&maxlst=".$hplans['email']."&maxsql=".$hplans['mysqldatabases']."&maxsub=".$hplans['subdomain']."&maxpark=".$hplans['parked']."&maxaddon=".$hplans['addon']."&bwlimit=".$hplans['transfer']."&cpmod=x2&customip=--Auto+Assign--&msel=n%2Cy%2Cunlimited%2Cy%2Cunlimited%2Cunlimited%2Cunlimited%2Cunlimited%2Cunlimited%2Cunlimited%2Cunlimited%2Cy%2C0%2C0&contactemail=".$vbulletin->userinfo['email']."";
If anyone can help me out with the other web host managers I'd really appreciate it.