For the most part, I'd probably just lean into typical roguelite meta-progression
>Several difficulty levels that unlock progressively (like Slay the Spire) so you have longer-term goals to work towards in the absence of PvP grinding
>New umas/cards are unlocked and upgraded over time via gameplay, with no gacha RNG involved
>Add in daily challenge runs with weird conditions/restrictions to give players more variety
>etc.
Then make the VN side of things way more involved, with more branching paths based on how well your uma's career goes (eg. having Nice Nature grow more confident over time if she wins a lot, instead of acting like she's a hopeless jobber even if you make her an undefeated triple crown champion)
I'd also probably remove the parent/inspiration system entirely, and compensate by adding some other way to raise your uma's track/distance/style aptitudes