In order to be truly agnostic, the graph language wouldn't even be able to presume anything about data types for the machine; it would have to take in a specification of the machine to transform the graph into the machine's code. But maybe that is the whole point - to stop the compiling at the point where the graph is produced, and leave all the optimization and transformatioin to machine code and load modules up to the system trying to run the code.
Add in some interesting module differentiation and OS caching capabilities for the compiled graphs, and you start ending up with some very interesting possibilities for cross program optimization and code elimination by the system, not just the graph transformation phase.
Ah, if I had a nickel for every bright idea I had - I'd still be poor. 'Cause I suck at marketing. :)