SFTP to FTP

I have an FTP server that requires a username and password.

 

I want to offer a service that uses SFTP to take those credentials and pass them to the FTP server (which is immediately "behind" the BigIP). (Just as one may pass HTTPS on as HTTP).

 

Is this possible / recommended and does anyone have any sample iRule code?

 

I am familiar with this article: https://devcentral.f5.com/articles/ftps-offload-via-irules but that focuses on FTPS and the mention of SFTP is simply to load balance SFTP.