What role should an interaction designer take in defining the product? In some cases, the designer is given all the parameters that the final product needs to have. The more parameters are handed down, the more the IxD's role becomes not only production, but a translation exercise. The solution that produced can only be as good as the translation. In some processes, this is intentional. "Request a wireframe from the IA and then pass it on to the visual designer". This then leaves project management as the cornerstone of the project in turn producing process centered design.
While is the issues seam painfully obvious, some companies end up in that rut. The main issue is simple, the end user interacts with the product not the project. The teams effort should be focused on the product, not the project. TImelines, resources and politics should be peripheral and should not drive the product.
So if the project manager is not in charge of the product who is? I propose that the interaction designer should own the project. They are the ones designing the end product and the ones that know goals and tasks that the user needs to be able to accomplish. Again, those points can be communicated to somebody else, but they become translations. This does extend the interactions designers responsibilities. They need to wok with business owners, end users, tech, QA, visual design, copy, etc. But the greater understanding of each of these with lead to a better product. Specialties can still exist and grow, but they should all live under one person that truly understands the product, FIRST HAND.