If they hadn't said no, then everyone would have array literals, argument declarations (no more need for argument 0, argument1...), More pragmas, preprocessor directives...That's pretty rough. If someone wanted to improve/expand things, I would have thought they'd be supportive that you are pushing the engine to greater limits.
I even designed the tool so anyone could write a plugin.
The one caveat is that it still had to look like proper GML, so it's not possible to add new syntax, just modify or extend existing syntax.
I'm trying to do the same with GMS2 now but so far no such luck. GMS2 would allow new syntax though, as the IDE still launches compiler when it thinks there is an error.
Sorry for hijack.