I think the answer to this question depends on the nature of the project itself. For instance, while engineers are important for the building part and setting of the project, limitations on what can and cannot be done, when it comes to designing something like a prosthetic the ideal personnel to tackle this design would not necessary be the engineer, but rather someone focused on the biomechanics spearheading the project. This would ensure the design of the device meets all the physical, aesthetic, and practical demands. Moreover customer input should also be noted to anticipate future failures from the products.