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.
Despite the stories about salespeople out on the road independently, sales is actually a team sport. Salespeople try to get customers on their team, for example. And they require support from marketing or servicing departments, to give the customer what they want. If you want the performance of this team to improve you have to get them all on the same page. Heck, many of salespeople’s most crucial problems occur because they are not on the same page with the customer, the support departments, or with each other. So, this could be a challenge. On the other hand, it might also provide needed motivation.