I fully support what you are doing, people might not want implicit infix math all the time. It also looks like you are thinking more toward how to let the user define infix operators, which my version doesn't do a good job with.
I actually rewrote my version in arc, except for 2 lines in ac.scm (one which implemented something pg was already thinking about, and one which allowed (eval (list + 3 4))). I posted a comment about it on my original post, but I think it got buried so far down that no one ever saw it.
