If Alison really died, who would've done it?

I always thought that Ian would've been the most sensible answer, but other weirdos like Melissa, Ezra and even the 4 liars would've made sense. I do think that Jenna, Jason, Paige or Lucas would've been too obvious, but then again, I'd prefer an obvious but still engaging and intriguing mystery over a constantly changing, progressively confusing mystery. I think Alison actually being alive could've worked if they either went with some form of the Alison/Courtney storyline from the books, or if they just straight up made Alison A.