With some fixes in the latest build Companion (see the release thread), and fiddling around with the vocab resources, I managed to get this working.
So here we have a parser-based VGA game with full source code (well, minus a few functions that fell back to asm), and you can compile all the scripts successfully (with the aforementioned release of Companion). I have the suffix and "tree" vocab resources working correctly now (it really was just a matter of assigning the right ones to the right resource numbers), so unrecognized words are handled correctly.
So this could serve as the base for a VGA parser-based game if someone wants to run with it. There are still a number of missing scripts, of course, since a lot was stripped out for the demo. But presumably these could be taken from decompiled game sources from around that time.