Getting your wider team, and your customers on-side is one of the key skills in complex B2B sales. No single person should attempt to play all the roles any more than a Goalkeeper should be found out on the left-wing in attack. 

With smaller deals it's possible that a sales person can develop a methodology where they can refine and repeat a process, relying on similar materials. However, with big-ticket sales, the whole team will need to communicate and pull together. It is essential that each player on your team knows both their role and the game-plan. Typically this will involve Business Development, Marketing and experts in technical aspects that the client needs to understand. 

It is important to establish how to address an opportunity at each stage, decide what to communicate and then choose the right tool for the job. 

If you have a good team and a good plan, closing business (winning) is just a matter of time.