You DONT have to rearchitect your processes to be CMMI compliant

I'm still surprised at how many clients have the misperception that they have to rearchitect their processes to be CMMI compliant.  There is nothing in the model that says you have to contort yourselves into some CMMI shaped box to comply with the guidelines in the model.  In fact, it's nearly impossible to do so and still carry on with your business model.  The CMMI is written as functional stovepipes (in alphabetical order), and your company processes, in all likelihood, are written to accomodate your business pursuit and delivery lifecycles.

The real trick to becoming CMMI compliant is to capture all of your business and technical processes, arrange them in some reasonable lifecycle order, then map that order to the CMMI to see where you have adequate model coverage and where you don't, develop a set of plans to address the gaps, and finally implement the plans to close the gaps.

If you have one monolithic Project Management process that addresses all the practices in the PP, PMC, IPM, and RSKM PAs, so be it.  Don't go rearranging everything to match the model.  Put together a mapping matrix that allows you to keep everything where it is, while at the same time allowing you to check yourselves against the model's guidelines.