As I said before. I could see a plot for the sequel in the shale of ED Regeneration VG. Which makes sense.
Mia is placed in a mental institution.
The police seize the Necronomicon.
Somebody interested in her story reads from the book and brings back the Deadites.
The institution or the town fills with Deadites.
Mia escapes and goes on a killing spree. Her soul after the first movie being connected to the demon has made her stronger...which also splits off creating Evil Mia.
The ending has Mia read the incantations and sends the Evil back...but also sends her a to a different place...be it time period, dimension or even universe...where she meets Ash
I can see where that would be interesting, but I would prefer to keep it rustic and in the mysterious lands of the woods. Keep it grounded for another movie, then have Ash show up at the end of that one, after AOD2.
I imagine something like Mia wandering the woods, trying to make it back home, constantly losing blood. She's delirious and confused. She passes the car from the first that she drove into the water. As she makes her way through the woods, she comes up on the same cabin. Everything is the same, only the cabin is not damaged. The jeep is there, tipped over. Everything is the same, with the exception of the fire damage. She panics and runs back into the woods. She again, passes the car in the water again (angled the opposite way of the first pass, showing that she is passing it in opposite directions). She again gets to the cabin, same set up. Everything is the same, only no fire damage.
This would set up the idea that while she thinks she's free and safe, the demons are still tormenting her, giving her false hope. This also gives the opportunity for the sequel to be a similar tone to the first, but more psychological.
From there I'm thinking have her family come up after not hearing from them on the detoxing, only to find David and their friends murdered, Mia sitting in the cabin floor, crying without her hand, bleeding out and in shock. They try to rush her out from the cabin to a hospital, obviously can't get away, and the nightmare starts again.
With the sequel they should attempt to do humour.
While I liked that concept for Evil Dead 2, that's a BIG no for this sequel in my book. If they indeed plan on combining the storylines, keep this one horror based. Let Raimi's world be a little more slapstick, while still scary and have Fede's be straight horror. Then, as they combine for a potential Evil Dead 7, go with a film that's about 85/15 horror. A ratio like Drag Me to Hell, but better, and the scary scarier and the funny funnier.