(IDE/Glulx) Provide debugging/performance-testing interpreters for Glulx
Provide special versions of the (glulx) interpreters that could help isolate performance problems, etc. I know that David Kinder has made special versions of interpreters to test, say, the time required to draw individual images; with some work and forethought, this kind of thing could potentially be expanded (hopefully in an accessible way) to allow folks to run down issues that otherwise can be difficult to isolate. The Mac version of the IDE currently has a natural UI to choose between alternative interpreters in the preference menu option to choose between glulxe and git, so the major issue with this would be developing suitable interpreter(s).
Ron Newcomb commented
... and expose the callstack, for run-time problem diagnosing. :)