I just used your snippet to create a classpath file
With a change made to Lumo (unpublished) and the most recent version of Mach, you can do: #addcp "cp"
this dynamically updates the Lumo classpath to use what's in the relative file classpath
another change to Mach has made it so adhoc requires work.
@jonpither awesome, I saw the commit on master and will try that out