The article does a nice job of identifying that there are multiple factors to consider in building and fine tuning this model.  I do however, want to add some factors that I think deserve note as well.  The skill sets and missions of the people doing the work are connected but not the same.  The article acknowledges scenarios that involve more or less “sales” work and this is certainly true, but I would suggest that the work the CSM does is in support of sales work and not “sales” work.  Yes the CSM should identify opportunities for growth and pass those to a sales person,  but the mission of the CSM is to drive successful use of the platform so the sales person’s job is easier in terms of closing renewals and pursuing expansion.  For me the line is drawn at commercial activity.  As a CS leader I do not want the customer to ever wonder if the CSM’s guidance is driven by a personal financial reward.  So I support a partnership between an AM and a CSM that identifies the skills needed for each role and then supports and trains the development of those skills that result increase the success they have in meeting their mission.  Sales skills and CSM skills overlap but are not the same.

@pat_kelly, we have discussions brewing in this regard that you may be interested in