There are numerous software services companies/provides those help in building PoC’s , prototypes, Products such as making MVP to recurrent releases. To provide such services one needs to have few key elements e.g. (a) engagement model i.e., fixed cost, T&M basis (b) software development process to follow i.e., agile i.e., capturing requirements, breaking into outputs & tasks (c) Tracking tools and delivery process (e) more importantly the Team i.e., the technical ability to provide the services. Also, the software service providers need to have the contingency plans e.g., solving high attrition, building bench strength, building excellency in the new technological areas/domains i.e., making the team ready for next set.
I have been leading the software services for last 18+ years in many companies and have started our start-up recently. We are now almost 16+ employees, which currently not matching your requirement of your research, but could I be useful if needed.