CWO = Chief (in branches other than Navy)?
We refer to our WO as "warrant" (as well as Sir/Ma'am, of course) because our senior enlisted are Chiefs.
In the Army, a W1 is known as "mister" (in the same way that one would refer to E5, E6, E7... as "sergeant). You don't become a "
chief warrant officer" until you become a W2, at which time it is traditional to be addressed as "chief."
However...
Practice often deviates from doctrine. In the 160th, for example, I often heard warrant officers of all ranks referred to as, and refer to each other as, "mister," regardless of rank. In fact, that seemed to be the preferred term. I've also heard many people (particularly those who don't work with a lot of warrants) refer to W1's as "chief," much the same way a medic is often referred to as "doc," even though that medic does not have an MD and is not, in fact, a doctor.
Also, at my interview board for the 160th, a CW3 (who I had actually knew prior to the board) asked me a question and I started my reply by saying, "Well, Chief..." and I was immediately cut off by the asshole Reg. S1 (a major), who said, "Chief? What do you mean, "Chief," do you see any feathers in his hair? No? Then why are you referring to him as "Chief?" //he was likening the term chief to Indian chief// (me, in my internal monologue of course --> "Well, because he's a CW3, which means by definition he is referred to as "chief," and since I've dealt with him several times prior to this, and called him "Chief" every time, if it bothered him I'm sure he would have said something to me about it by now. Asshole. Sir."
) So sometimes it's better to find out what a warrant wants to be called before applying a standard template.
I'm about 75% through the book and it took me a page or 2 to realize I had the characters and plot line from your case study stuck in my head... I should have listened when everyone said, "just wait 'til you hit 30 and XYZ happens". 
there are also references to at least three members of the site in this case study.
