Planemo machine used to include Codebox - which was a huge pain and didn't work well and is now a dead project ... ... but bundling a Web IDE would make tool development could make the Cloud image product easier to use - files could be managed and tested from a web browser. This would also probably help people on Windows using the container.
I looked around again and http://codiad.com/ seems to have some small signs of life - including a recent update to their ace dependency - which is actively developed.
Alternatively - we should also pursue hosting a VNC application with a web frontend from a container. Here is an example xubuntu VNC Docker application - https://github.com/amitsudharshan/xubuntu-desktop-docker. They don't setup a web application to use it though - like http://novnc.com/info.html.