Okay, this post was made more so in light of the most recent update, that being the Cid Raid.
What I was thinking was less like other ATD games and more unique. Instead of doing a flat pity for units / familiars. Instead, lets say after 10 attempts, make it so every time you beat the stage, your percentage chance to get the unit / familiar will go up by 0.5% up to a max of lets say 5-10%. Of course when you get the unit / familiar the drop rate buff will go away to make it more fair.
Keep in mind this is just an idea and these numbers can change to the devs liking. I just think this was a unique way to keep rates low for the lucky people who get it in 1-4 runs, while also benefitting the people who grind hours and hours for this stuff.