I still hope to see them consider tweaking the scaling to be organized into tiers. So like:
Tier 1 = Bunny, Juliette, Red Battler, Ankyo
Tier 2 = Agate, Arcana, Kimie, Shehera
Tier 3 = Jennie, Rumiko, Sung, Solveig
And so on and so on.

And they'd have to slot event girls and pachinko exclusives into appropriate tiers as well (either for being dropped by a particular boss during an event (although that would put a disproportionately high number of girls into tier 2 since so many events have used Dark Lord for one of the drops) or for fitting into a particular world's theme (so for an example Shao from epic pachinko could be tier 3 since she fits in with world 3's ninja theme, and variant forms of a girl could all fit in the same tier as the original form instead of going with where the variant dropped)). Or at least try to sort them out that way as much as possible.

And I suppose maybe order could scale them somewhat from their tier's base cost rates? So for each specific tier there would be a base requirement and a base cost for reaching 1-star and for paying in the 1-star scene (additional stars being whatever % increase over those bases), and then maybe the first girl in your list from within that tier starts at base x 1.05^0, the second starts at base x 1.05^1, the third starts at base x 1.05^2, etc.

With or without that bit of scaling within a tier, the scaling of the tiers themselves would achieve the same goal which the devs had stated was intended with 2.0's scaling. Which was for it to be very easy for newcomers to get into the game and for it to get progressively harder as players get deeper and deeper into the game. But it could rein in (and somewhat future-proof) the growth of the costs compared to what we're seeing with the current scaling. (Especially if earlier tiers get more heavily populated than later tiers do.)