With a simple modification we can have a wildcard in our website subdomain.
You want this, wildcard subdomain: *.example.com redirects to example.com
Go to: Sites -> Websites -> Subdomain for website -> Add new subdomain
Redirect Type: No redirect
Then ISPConfig will generate "example.com.vhost" with:
Test it and use at your own risk.
I wait that this little patch could be included in next release. Only it allows * in regex domain verification. I use it in my production servers (Debian 5).
# wget ...
# cd /usr/local/ispconfig
# patch -p0 < ispconfig3_website-subdomain-wildcard.patch
I saw a post with a different solution.