If we were to get a second Yuuka game, i would like her to be the main playable protagonist. With a battle system, of course, alongside the usual exploration mechanics. I'd also like to see her be subjected to "battle fuck" attacks. Of course i'd also like to see a "virgin run", as well, just for extra challenge.
If there was one complaint about Amazon's Yuuka content, is that she doesn't actually feel like THE Kazami Yuuka, from the Touhou series! Maybe the combat, might actually be her spell cards.