The leader can exchange the mats in the material vault, it does not take much work, when you exchange you do lose half of the mats, it would be nice if other officers such as the Director and maybe Marshals could exchange materials when they fill up and the leader is not available. I have on many occasions taken my mats down to zero while working on leveling the base. Now I regularly take them down to zero because I do not need them. Also if you level your Material Vault it holds more. Another possibility is maybe add the various building materials in the Base Manager goods, so they can be purchased, and turned in like the materials you get from quests.