Plot Twists in Remasters

I've been thinking about plot in ROM hacks, which are basically fan remasters, partly because I'm procrastinating on town exterior maps and partly because I need to do some sprite work, for which a character's plot is relevant.  This brought my mind around to direct sequels and remasters.  When you remaster a game, you basically present a familiar scenario in an unfamiliar way.  Because of this it is effectively impossible to surprise the player.  Thus, your only outlet for surprise is presenting an idea in a novel way or creating shock with a change they did not expect.

But how do players react to that?  How far can we deviate from what the audience expects before it irritates rather than surprises?  I want to discuss character changes.

(1) Survival
A character dies in the original but lives in the remaster, or lives in the original but dies in the remaster

(2) Morphology
A character is younger or older than in the original, or their gender or physical characteristics are changed

(3) Temporal Scenario Displacement
A character is present earlier or later in the story than they were in the original

(4) Morality
A character who was antagonistic in the original has a more complex or even beneficial role to the party in the remaster.  Unplayable characters become playable



Let me pose these another way, as questions about the Final Fantasy series.
(1) In FF5, what if Galuf survived but Reina perished?
(2) In FF4, if the Feymarch didn't accelerate time, should Rydia be a teenager in both Mist and Dwarven castle, or a child?  If Rydia is a child, should Edge be a child too?
(3) In FF6, what if Relm was recruited on the Lete River, or the Veldt?  Would you want her to leave the party and have a 'vanillish' reintroduction at Thamasa?
(4) In FF1, what if Princess Sara was one of the Warriors of Light?  What about Bikke the pirate?

Basically, what do you expect to remain unchanged in a remake and what changes would you tolerate?