Yeah, I probably wouldn't use it for that either, at least as much because of the relative instability and hackishness of arc. It was fun for a few minutes to imagine modifying it to be used that way though.
No, I was forgetting that ac is considered a compiler :) But it compiles the Arc codebase every single time Arc starts up. Maybe we should start memoizing its outputs to disk somehow, see if that makes it noticeably faster. My suspicion is egregious runtime processing like ar-denil-last and ar-apply-args will cause it to not make a difference.
Given the pervasiveness with which Arc has to make such transforms at runtime, I've gotten into the habit of thinking of it effectively as an interpreter.