The seeds of the CW5, or MW5, grade were planted at the height of the Vietnam War. When I entered Flight School in Nov 65 a good percentage of the WO Candidates had graduated from HS earlier that year. They enlisted for Flight School and after Basic Training were at Ft. Wolters beginning flight school. I was sort of in the middle with three years prior service. We had one 1SGT begin with us but had to drop out. There were many SSGs and SFCs.
In 66 the TIG required for promotion from WO1 to CW2 was being lowered from 18 months to 12. As Vietnam wound down, W3s were coming up for W4 with 10 or so years in the Army. Had I stayed a Warrant I could have come up for W4 with 13 or 14 years in the Army. A guy wanting to stay for 30 could have spent over half his career as a CW4 had they not created the W5 grade.
I stayed at the SFC level for seven years (NG) and finally made MSG in 1988. If I hadn't made MSG, I'd have gone the warrant route. Three years later, I made SGM and have been that ever since. There is no way I want a CSM postition, since it's the same pay and many more problems.