Ability to Access Webmail using Subdomain

The current scheme (as of IW 4.7) to access Webmail is to use the domain followed by a / and then webmail, thus if your domain name is
happytimes.com you would access webmail using http://www.happytimes.com/webmail

This is all fine and good, however, I would like to use SiteWorx for email for some of my cPanel accounts. And I would like some capability to point the MX record to the SiteWorx account as well as the A Record for webmail. Thus the need, as I see it, instead of webmail being access like this:
It would be accessed like this:
This would help resolve a lot of issues.
OR Both would be good as well.

Hi just a suggestion to get around this limitation:

You could create a happytimes.com Siteworx account on the InterWorx server with either a pointer domain or subdomain for webmail.happytimes.com.

Then, create a webmail.happytimes.com and mail.happytimes.com A record on your cPanel server pointing at the IP of the InterWorx siteworx account. Also make an MX record pointing to mail.happytimes.com.

When your clients visit webmail.happytimes.com you could either redirect with a .htaccess file or alternatively have some sort of portal/splash page for the 3 webmail clients. This is also nice because horde, squirrelmail, and roundcube will be accessible at webmail.happytimes.com/horde, etc…