Staff augmentation vs. project work in A&D are really two different companies. Another key segmentation is work that requires certification (NATO Clearance, secret clearance, Airbus/Boeing training, etc).
On staff augmentation, a lot of young firms start off bringing in good ex-employees of the majors and and targeting the supply chain. Often the majors Boeing, Dassault, etc like it when subs use talent that already know the primes practices.
If you are targeting project work, you need to define if you are selling skill or price. If your the best team for converting major assemblies into a stream line lean process, you need to clearly define that and sell it into the targets.
In all cases, you are likely to get your first customers in the supply base. The supply base is likely trying to win a bid or execute a current contract. They want to mitigate risk using temporary labor, especially if you are in a EU labor market.
If your model is to sell outside of the Primes, for example selling aerospace talent to boat manufacturing, I would stick more to project work with a few key initial clients. Create an iconic success. I would also look at the UAV market. There is a lot going on there. Often the people creating UAV's are more controls focused, they might like having someone else be there air frame team.
I was heavily involved in the lean manufacturing movement at McDonnell Douglas and Boeing. Mostly on F/A-18, but also C17, 787, UAVs, etc.