Part of the goal of the player is to expand the Mother Base too, which requires builders and resources. By adding men to the squad, it opens up further Mother Base upgrades, making each platform grow taller and also fast tracks the processing time for the materials needed to build the expansion.
Materials can actually be discovered in most enemy outposts so if the player wants a big payday, he may consider investing in a multi-balloon Fulton to lift entire shipping containers of the things needed in the construction. The container color actually tells the gamer what goodies are inside.
There is also a high-level support team to ensure faster delivery times of needed supply while the player is in battle like when he runs out of ammunition or getting too much fire from enemies, bullets actually drop from the sky. But he needs to be wary when the big crate drops.
The player also has access to a research and development (R&D) unit which shall be able to work on improving battery life, giving extra Fulton functions, and radical new designs of the cardboard boxes use by the player for cover.