As stated in my subject, having the option for one domain to use the same FTP or SFTP listener as another domain would be ideal.
I have read this forum topic, http://www.wftpserver.com/bbs/viewtopic.php?f=4&t=750, and understand your design process. Your current mechanism would also allow different domains to have the same usernames since you're using the listener as well to know which domain to use but I think it would be good if you had an option where different domains used the same listener for FTP and SFTP, then denied someone from creating an account with the same username across the different domains.
The reason is this, I don't have another public facing IP address to use on the same host, and with the people I'm dealing with getting them to use a different port would be confusing for them (trust me, I've been down this path), since using Filezilla and choosing SFTP when setting up site automatically uses port 22, and then even in the instance where a user understood how to change ports in the Filezilla, most would need their network administrators to allow a non-standard port to pass through, (again I've been down this path as well).
Now, why i'm using different domains, is for ease of user account management purposes across our companies.
Hopefully, you'll consider this. If I've lost you along the way then let me know and i'll try to explain better.