Cassandra is one of the characters in Mafia 3 that can provide you with many different upgrades. In order to unlock them, you’ll have to help her and give her control over more districts in the city. Cassandra’s upgrades comprise of numerous weapon enhancements and operator favors that allow you to temporarily shut down all phones in one area.
Different lieutenants provide different upgrades. For example, Cassandra can upgrade your guns, Vito will increase your health bar and Burke has explosives for sale. The more money each of them makes, the more upgrades you unlock.