The Àrnadalr Experiment

Plot
mmm okay so like, what if Anna.1 and Elsa were twins but they actually looked different. Like, they look like their film counterparts? The Queen actually does live forever by use of a drug-cocktail thing derived from Anna.1's cells. Elsa still "kills" her sister but like, yeah... And then Anna.2 is created to get back at Elsa/lure her in/destroy her. And the rest of the story is still the same, the differences being that bit of backstory, and instead of Elsa having to reconcile the fact that the girl looks like the person she has been trying to kill for 200 years, instead she has to come to terms with the fact that she's been tasked with killing the one person she only ever wanted to save (so, Hans still tasks her with killing Anna but she doesn't know what the target looks like until she's there).

Once Elsa realises, she knows she can't kill Anna. They have to go into hiding while figuring out their relationship and a way to destroy Hans. They sneak back into the castle and learn that he wants to kill the queen and take over the 'world', as it were. He wants the power that she has.

Elsa
She wants to kill the Queen for a few reasons, first and foremost is because she blames her for Anna's death. She met the Queen a few times as a child b/c the Queen (omg shortened to TQ) was like, an intern at the time and took a special interest in the twins. She also takes it out on TQ because she //knows that she killed Anna.1 and can't bear the guilt of it. Part of the reason is because of the still-occurring experiments and 'hybridisation' of people.

Anna.2
Brought up believing that Elsa is her Guardian Angel (of sorts). Has problems reconciling the girl of her dreams and the girl in front of her. She refuses to help Elsa at first until their first brush with death wherein she's held for ransom and //Elsa, not TQ, comes to save her.

Hans
Basically, wants the power TW has. Is in cahoots because they both want Elsa's DNA. Her ice-magic is very dangerous—she killed her own //sister—and the regenerative powers are out of this world. He's actually been planning this for a while; the 13th son of a powerful Scientist working for the queen. Brilliant but invisible, he wormed his way into her good books, stealing her serum from the tender age of 9 and slowing his own ageing considerably. TQ thinks nothing of it—actually, it was Hans' idea to create a clone of Anna. He's at least 30 years old, though only looks about 20.

The Queen
Wants Elsa because her DNA holds the non-dormant aspect of the regenerative gene. With it, TQ can not only slow down but potentially reverse her ageing. And, she can find some way of harnessing the ice-powers as a weapon, and put an end to the 200-year war that has been ravaging the Outer Kingdoms. Basically, she has power. she wants more power. elsa is the key to getting that power.