Currently, only a subset of command-line flags (mostly those specific to JRuby) can be configurable by JVM properties. Others, like debug mode, verbose mode, and so on should be configurable with properties as well.
@headius not sure if I understood it well, do you have an example of what is a "configurable jvm property"? I can look into that.
Actually I have this almost complete...thanks though! :-)
Fixed this in 7a883f1.