People have wanted Tifa as the... replacement, but this both is kind of weird (why does a love interest have to replace a love interest... what?), but also is nonsensical as Tifa in FF7 is driven largely by the fact that she knows Cloud is incredibly unwell. If she dies early, then her entire character arc like... doesn't exist?
I do think that keeping Aerith alive in FF7R would add a lot to the game, but Tifa and others don't really make sense. Barrett and Red XIII are the only two characters that have somewhat completed character arcs but Barrett is a more important character in Discs 2 and 3. Build up Cloud's relationship with Red XIII and Red XIII's friendship with Aerith so it can make sense for Red XIII to sacrifice himself for Aerith and so that Cloud is still emotionally distraught.
But Tifa makes no sense as the "replacement."
I do think that keeping Aerith alive in FF7R would add a lot to the game, but Tifa and others don't really make sense. Barrett and Red XIII are the only two characters that have somewhat completed character arcs but Barrett is a more important character in Discs 2 and 3. Build up Cloud's relationship with Red XIII and Red XIII's friendship with Aerith so it can make sense for Red XIII to sacrifice himself for Aerith and so that Cloud is still emotionally distraught.
But Tifa makes no sense as the "replacement."