To implement my hacks I've already needed to pull a few pieces of the Arc compiler up into Arc, such as ac-denil and ac-global-name. So the direction this is heading in is to make parts of the Arc compiler available in Arc: ac-denil, ac-global-name, ac-scheme.
This allows us to do various powerful things, of which one is getting at Scheme functionality easily.
You could then write a plain "mz" macro that expanded into "ac-scheme" directly, or, if you wanted, a more sophisticated one that did things like giving easy access to global variables in the expansion.
The "scheme" part of the name is a visible reminder that the code inside is literal Scheme code instead of Arc code.