I feel like, even with just 5 units, this really breathes new life into the game. I'm kind of actually excited to log in to the game and play around with the upgraded units.

Now, I don't think every unit needs to be meta defining, but it should at least be close. The units we use should be more about flavor than strength. They could run it like they did 7 star awakenings, and have a new batch every month.

*Edit. What if option 4 was a permanent addition? Every month we vote on a unit to upgrade, then the next month the winning unit gets upgrades along with a new vote. Keeps up engagement and interest among players without hitting the banners too hard.