>>544096838
>Increase vigor regen rate and/or resource drop rates
Introduce something like the cafe system in Blue Archive. In Blue Archive, the cafe provides another source of AP other than natural regen. As you progress in missions, you get cafe upgrade items that increase AP gain.
At base Blue Archive gives the same amount of stamina that Stella Sora gives a day: 240/day (10/hr), but if you include max cafe upgrades you make over 1k stamina a day (not counting daily mission rewards, or other sources)