I believe that design input should generally be managed by the marketing team, this is because these individuals have the knowledge to know what is in demand, and therefore will design a product that will sell and make money. However, although the marketing team has to set the design needs, it is the job of the engineering team to report back and say what can realistically be done. If everything the marketing team suggested can be done then great. If there are certain things that cant be achieved then now the marketing team and engineers have to work together in order to produce a functional project that still sells. Notice in the beginning I said “generally” and that is because there are some special occasions in which there will be more people added into the process. For example, as some of my peers have said above, when building a prosthetic the needs of the customer are taken into consideration as well.