I’d like to build a profiling version of Gnusto. Now what would be really helpful is if inform (6) could output to a file the names and offsets of every function, including the veneer. Is such a thing already possible?

You can get that information in a variety of formats: have a look at the -k and -a switches. Glulxe can be compiled with profiling support: have a look at how the script (that comes with Glulxe) does it. Note that the documentation in isn’t quite right: the -a switch now does output veneer functions (in the latest Inform 6.31N).