The "plan MDM, start CDI" thing has become a modern-day IT aphorism because MDM is difficult, and big, and thus invites the same risks as any ambitious program, namely analysis paralysis. By the time you guys (or your consultants) come up with your "MDM Strategic Plan and Vision, Version 1.0" everything will have changed. That's why we recommend doing a limited amount of up front planning for MDM -- including some initial application alignment and data identification -- and then launching a Small, Controlled Project (SCP). The SCP is very often a CDI effort. Why? Because customer-focused programs have the most executive visibility and the highest need for integrated, cleansed, reconciled and propagated customer data (read: CDI).
Yes, it's more complex than simply establishing an MDM vision and buying a CDI hub, with lots of work in between. The point is to show value early and often, creeping toward eventual MDM mastery.