I don't know what your planned abilities are or how you want the game to be played, so I'd need more information to be able to help with that.
After the first stage I recruited two allies, which happened to be a rapier girl and a healer, and I just invested into the former. As I played I eventually chose +2 Allies twice more, and didn't get any Shield guys.. So I had my first rapier girl with three Defense upgrades, one HP upgrade, and one Attack upgrade before I realized that 5 upgrades was the max. 6 Attack was enough to one-shot most enemies, 3 Def (and 9 HP) was enough to not get killed in a round since no matter how many enemies there are, only two attacks can be made.. But there also was a lot of strategic use of the bushes, often staying right behind bushes so enemies have few or no avenues of approach, and sometimes I'd dart out, kill the two nearest enemies, then move back to safety.
From what I played, I don't think any enemies had ranged attacks? And maybe it was just that stage that I played ~4 times that had a lot of terrain in your favour? So maybe there are a number of factors which could make the game more strategic even without modifying the action system.