Our Service/Consulting firm's core focus is UI/UX Designs, and Frontend Engineering. We tend to get quite a bit of incoming work that are not in our core focus. We started working with other partners. We either know these partners or are introduced to us. We interview them, talked to them, worked with them (vetting them).
Our clients know that they can go on a vacation while we work on their projects. They wanted that same experience while working with the partners that we introduced. So, we end up handling the client's project and make sure it gets done via these partners.
Work Sigma is borne out of this patterns, and process that we followed. We want to grow this, formalize it, and be able to provide a good service to clients and make them happy. One of the marketing taglines that we tossed around our team is, "Agency in the Cloud".
btw, A friend told me there is something similar at UpWork - https://www.upwork.com/pro/. This is nice - the market is tested and proven.