When establishing the relationship with an external service provider (outsourcer), why do we document a whole operating model spanning both organisations? The whole point of outsourcing is that the supplier should be a black box, with inputs, outputs and performance requirements. What we need to define is the interface between the two entities, to ensure the operating models of each one mesh properly together. Define the connecting cogs, or the plug-and-socket - choose your analogy.
This is more efficient: we don't redundantly document processes which already exist, and are documented elsewhere. It is more effective: we focus on the gaps, specifying the requirements for change in each organisation in order to connect their operating models.
It seems this is pioneering stuff: there is very little published on what an engagement model should look like or how to develop and use it. So I built one.