TomC is now looking at supporting the JON embedded console within the ESB project, so expect this to progress over the next few weeks.
The current plugin code was written for the JON server which is shipped as part of the SOA platform and may contain extensions not available in JOPR. TomC will be able to comment further on this.
The plugin should work in JOPR. I'll try to sort out any dependencies like the FileUtil class you mentioned - if you want to file a bug on it, it would help.
Thank you for looking into this.
I have created a bug report here:
I have set the severity to Minor as the actual functionality of the ESB itself is not impacted.