For what it’s worth Ryan, I’ve just sent a Pull Request to Marlin to use “Modal move” (or “Sticky move mode” as I call it).
It allows interpretation of G0/G1-less code, where only the “current move mode” parameters are sent on each line.
The PR also implements “parenthese” comments.
With regard to Z feed speed, I wonder why we don’t limit the max Z speed in the firmware to what is physically possible on that axis ? Doesn’t that limit apply correctly and cap the move ?