When responsibility for selecting critical marketing metrics gets delegated by the CMO to one of his or her direct reports (or even an indirect report once- or twice-removed), it sets off a series of unfortunate events reminiscent of Lemony Snicket in the boardroom.
First of all, the fundamental orientation for the process starts off on an "inside/out" track. Middle managers tend (emphasize tend) to have a propensity to view the role of marketing with a bias favoring their personal domain of expertise or responsibility. It's just natural. Sure you can counterbalance by naming a team of managers who will supposedly neutralize each others' biases, but the result is often a recommendation derived primarily through compromise amongst peers whose first consideration is often a need to maintain good working relationships. Worse yet, it may exacerbate the extent to which the measurement challenge is viewed as an internal marketing project, and not a cross-organizational one. Measurement of marketing needs to begin with an understanding of the specific role of marketing within the organization. That's a big task for most CMOs to clarify, never mind hard-working folks who might not have the benefit of the broader perspective.
Second, delegating elevates the chances that the proposed metrics will be heavily weighted towards things that can more likely be accomplished (and measured) within the autonomy scope of the marketing department. Intermediary metrics like awareness or leads generated are accorded greater weight because of the degree of control the recommender perceives they (or the marketing department) have over the outcome. The danger here is of course that these may be the very same "marketing-babble" concepts that frustrate the other members of the executive committee today and undermine the perception that marketing really is adding value.
Third, when measurement is delegated, reality is often a casualty. The more people who review the metrics before they are presented to the CMO, the greater the likelihood they will arrive "polished" in some more-or-less altruistic manner to slightly favor all of the good things that are going on, even if the underlying message is a disturbing one. Again, human nature.
The right role for the CMO in the process is to champion the need for an insightful, objective measurement framework, and then to engage their executive committee peers in framing and reviewing the evolution of it. Further, the CMO needs to ruthlessly screen the proposed metrics to ensure they are focused on the key questions facing the business and not just reflecting the present perspectives or operating capabilities. Finally, the CMO needs to be the lead agent of change, visibly and consistently reinforcing the need for rapid iteration towards the most insightful measures of effectiveness and efficiency, and promoting continuous improvement. In other words, they need to take a personal stake in the measurement framework and tie themselves visibly to it so others will more willingly accept the challenge. There are some very competent, productive people working for the CMO who would love to take this kind of a project on and uncover all the areas for improvement. People who can do a terrific job of building insightful, objective measurement capabilities. But the CMO who delegates too much responsibility for directing the early stages risks undermining both their abilities and their enthusiasm -- not to mention the ultimate credibility of the solution both within and beyond the marketing department.