Part Four - Zankou
This part sees Henry come in straight away (or perhaps Glenn's return) as well as Paige doing whitelighter duties as she did in the real series, possibly returning to social working.
Phoebe, who is now married to Drake, becomes impregnated by Drake but doesn't shy away from her Charmed duties, probably the most likely innocent saver (as Paige is with her charges).
Piper, with Leo as her project manager (something he might even take up professionally) extends P3 into a restaurant.
We'd love P3 to also have some kind of significances as well, instead of the Nexus, Zankou could be after something within the club (immortality amulets/stones perhaps). He realizes that the only thing that can stop him is the Power of Three, so he kidnaps the only one who doesn't have active powers - Phoebe - although the other two manage to get her back.
In a big fiery vanquish, the sisters risk their lives, fully expecting to die, but Paige manages to panic orb away. Piper and Phoebe are left for dead but using the spell that Chris gave them, Paige does a Forever Charmed and goes back in time to save them, in a less selfish fashion. She never goes forward so we never see any of the Charmed Ones as old.
Paige gathers Grams, Patty and perhaps Prue to help save the day. Paige phases back into her body as soon the group arrive.
Patty freezes Zankou as Grams (or Prue) TK's the amulet away from Zankou and then Piper blows him across the room. Now unprotected by the amulet, the family recite the Source vanquish spell and then the sisters saying the P3 spell to protect them all from the explosion (which of course was what killed Phoebe and Piper first time around).
In happy ending, Piper, Phoebe and Paige walk down the stairs together, admiring the photographs on the wall as we get flashbacks of the past significant to each image, ending with the picture of the original Power of Three. Then there's a bit of magic and Paige becomes a part of it, too.
We don't see the future at all...
Primrose Empath, Esmeralda