Design brings great value when you apply its mindset, skillsets, and process to spark new ideas, thinking, concepts or to deliver specific outputs as part of a larger program. It can play a key role in problem reframing workshops when you want participants to take on a designer's mindset and question fundamental assumptions. The mindset and process can also come together to establish a common base from which to increase buy-in and participation. And a designer's skills can always help to strengthen collaboration by helping key stakeholders to visualize a process and understand the important role that they will be playing.
When choosing design as a spark, you're are probably more likely to contract an individual design consultant or look for design skills that a more traditional partner has gained in incorporating design into their work. Sometimes that means that you need to rely on stakeholders who while invested in design may not have deep expertise. At the same time, this is a good way to learn about design and to start to see it in action.