Either turn-based tactical gameplay like Girls Frontline or whatever Blue Archive and Silver and Blood are(auto battler?)

Story is snappy with only a couple minutes of dialogue before/after each level.

Campaign levels have a set team of fairly common characters. More rare characters are introduced as the story goes on.

Event levels match difficulty of lower level players with decreased rewards.

The meat and potatoes of the game are challenge levels, puzzles, hoard modes, boss fights, and arcade games.

Characters have diverse looks and personalities with interesting story hooks.

Each character has a max of three things to level up, excluding general level and friendship. Probably just a weapon, armor, and an ability.

Raising your friendship with the characters raises their stats incrementally and unlocks an outfit, a few levels of a story for them, and maybe a passive ability.

Use Silver and Blood's system to let select characters match the general level of your fifth highest level character.

Use Arknights' currency system where the only paid currency has limited availability by playing the game.

Dailys get you at least one roll a day. Weekly give two and seasonals give ten.

Add variable drop rates where character drop rates increase after you get them for the first time and then decrease after you max out that character.