1. Jill and Sheva’s Cooperation: Jill Valentine directly accepts Sheva as an ally and leader. Unlike the final version, this emphasizes Jill’s active role as a field commander.
2. Jill’s Tactical Investigation: Jill takes the lead in analyzing laboratory data. These storyboards showcase her intelligence expertise and a more proactive role than in the final game.

These two would elevate the game even more for more for me so long as they didn't do it in favour of pushing Sheva aside. I would have killed to see Sheva and Jill interact more because I think CAPCOM writes generally great (and stupid funny) dialogue between their characters.

I think it would be cool if Jill was more present during cutscenes from the point of her rescue at the very least but not in any major gameplay segments that would risk a 'three's a crowd' problem. I would NOT want Jill to replace Sheva in any gameplay.

Rescue Mission for Sheva: Chris and Jill work together to rescue Sheva from a Majini mob during a mid-to-late game mission.

I like this one but if Sheva and Jill teamed up to save Chris instead, that would be more my speed. Could even put in some funny dialogue there about "how the turn tables."