if you could take away 1 minifig and replace it who would they be?

If u could take away 1 minifig and replace him who would it be. They must be from the same theme.

1. Roman(Series 6)----->athenian(silver/blue helmet)

2. Viktor krum(in the second task set)------------>Cedric Digory

3. Hermoine(in the second task set)------------>Cho Chang 4.