If your stage can generate items, then you can code the behaviour of collecting such item inside the characters, so Idon't think the infinity stuff is that problematic.
The ratio stuff could be a bit tricky, but then again it's just buffing a member of the team, kinda like the Leader system in KOF03/XI.
That’s when I thought, “good grief”
Just ain’t my belief
Until I saw the holes
Inside his hand