Frozen 2 was weird. They clearly had big epic ambitions, and then had all of it take place in one small forest glade and a single cave.
It is hilarious that Disney refused to acknowledge all of the discussions about Elsa being LGBT and then lit up the caverns in Frozen 2 with bisexual lighting coding and had her singing about the voice inside her urging her toward forbidden-to-society desires. (That said, she doesn't need to be gay or bi for Frozen to have tried to reject the idea that little girls should spend all their time thinking about being wives.)
Honestly, they need to bring in some DMs to help them with their world building. They've got interesting stuff with elementals, a gorgeous faux-Nordic/Sami setting, some information about other realms across the sea. Good D&D campaigns have been built with a lot less.
I think they could do more with Anna.
Or -- and this would freak a lot of people out -- do a time jump and have Elsa be a mythical figure, the long-lost Snow Queen (which is where all of this began originally with Disney) and have young heroes redeem her, after a heartbroken Elsa has fallen into darkness. (What would Elsa do if something happened to Anna? It probably wouldn't be great.)