It is possible with common units, though their units are usually at 50CC50 and maxed affection by the time they make video guides. This guy did the first map with the majority of his team being bronzes. https://www.youtube.com/watch?v=qeWa...QrUVpHUk7hCHeS
Here's his silver only guide for Base Scramble I: https://www.youtube.com/watch?v=ZYtYCyIMD4c