Kanban provides this kind of framework for improvement and I would strongly recommend such clients use it, as the basis for informed process development. As Henrik Kniberg points out in his companion volume to Anderson's, "Kanban and Scrum making the most of both", the methods are not incompatible. The fewer constraints that Kanban imposes on processes means that from a Scrum starting point, some of the constraints of scrum could be relaxed if benefit was deemed to flow from it. I presume this is why Schwaber objects to the method so strongly - if the starting point of the process is waterfall, one might end up with a slightly improved waterfall but not the major benefit that would flow from a true agile process. However if Kanban is followed effectively changes to a Scrum starting point would only be made if evidence was available for incremental improvements in the key business metrics. Yes there are risks involved in moving away from tried and tested agile processes. But that's where rewards lie too.
I'm not convinced by arguments between methods that focus on the character of those proposing them, when the substance of the methodologies are not examined. I expect more from the proponents in this case, more substance, evidence... and maybe a little more humility. Process improvement is not a one shot change from waterfall to agile. It requires insights from many different quarters to produce the best possible result for the business.