Online ftp text editor

Hi,

I am trying to build some sort of control panel for my game server hosting. I want that customers are able to edit the .cfg file online. I was thinking thati way be possible to setup ftp accounts with limited rights and put a text editor online that uses ftp, only i have realy no idea how i should do this.
Can someone help me? Or if there is a simper sollution i would be hapy to try that to.

The main goal is to edit a cfg file on my vps online.