Best destined ally for the most peak story potential?

I’m about to run CoS for the first time by minimizing the pool of destined ally.

My players only care about plot, lore and story climax so I’m willing to cut out some destined ally options for the sake of story. I’m willing to prioritize NPCs that would have more impact to the story over their combat competency. (My players might even like a weak ally so their final fight will be more challenging)

Imo my headcanon’s best ally is Arabelle (a homebrew version inspired by suppressed high potential powerful magic user trope - e.g. Ciri, Jean Gray, Wanda, Raven etc) due to her hidden blood ties with Strahd.

Other candidates:
- Ezmerelda
- Van Richten
- Mad mage (Victor Vallakovich from the future version)
- Sir Godfrey
- Arrigal
- Vasilka

Let me know what you guys think!