this is how I would change Charmed, even with the restrictions and budget cuts.
Season One: Rex and Hannah being the Season's big bads. They survive the events of Wicca Envy and Prue quits her job. In the last three episodes rex and hannah hire Rodriguez to expose the sisters as witches and cause trouble for them so they can steal their powers in midst of the chaos. Love Hurts ends in a cliffhanger with Rodriguez recording Prue using darklighter powers on Alec but Prue thinks Rodriguez is mortal and so she doesn't use darklighter powers on him.
The last episode begins with Rodriguez exposing the sisters and in the midst of the chaos Rex and Hannah, with Rodriguez help, steal Piper's and Prue's powers but Phoebe vanquishes them with potions. The sisters cast a spell to turn back time one day and they leave to vanquish Rodriguez and destroy the tape. when they get back to the manor they find Rex and Hannah there holding Andy hostage. They fight and the CO win but Andy still dies.
Season Two: the season would be exactly the same.
Season Three: the season would follow the same path until blinded by the whitelighter where the warlock Eames escapes the heavens and kidnaps Phoebe. In the next episode the Piper and Prue come to the conclusion they need Cole's help and summon him. Cole only accepts to help them if they promise to leave him alone until they cross paths again. Eames exchanges powers with Phoebe, turning her into a whitelighter and then poisoning her. furious Cole vanquishes Eames and rushes to Phoebe who is nearly uncounscious. While Cole is declaring his love for her Piper remembers that love triggers whitelighter's healing and casts the spell to exchange powers. Cole then heals Phoebe but he buntly denies his feelings leading to a bit of angst for a couple of episodes.
Season Four: the source is vanquished earlier and thus Cole and Phoebe marry in the episode eleven. The episode ends in a cliffhanger with Phoebe becoming evil due to the dark wedding (though only the audience becomes aware and the good guys remain oblivious). The Elders warn the charmed ones that a great flow of evil magic has started and that the Source somehow survived.
Cole starts to gather up an army with which he will invade the mortal world while Phoebe tries to hide her newfound demonic powers from her sisters. In the end the sisters find out about Phoebe being evil and that Cole is now the source. In the next episode there's a mixure of family angst while Piper and Paige try to gather an army of good witches and whitelighters to fight the Source's army. A battle issues in the Golden Gate Bridge (it's mostly a CGI version with only the part where the cars stand being real) with heavy casualities for the side of Good that is forced to retreat.
Piper and Paige try to vanquish Cole but without the power of three they are nearly vanquished. Piper begs Phoebe for help who's is torn between choosing her sisters or choosing Cole. As the battle unfolds and the side of Good is being slaughtered, Piper tells Phoebe to remember their sisterhood and the loss of Prue and asks if she wants to be indirectly responsible for the death of one of her sisters. Cole angrily tells her to shut up and throws a fireball, hurting Piper greatly. Shocked Phoebe traps Cole in a crystal cage. They then cast the spell to vanquish him and Phoebe looses her demonic powers.
Season Five: Season Five deals with the direct consequences of the battle. With many witches and whitelighters dead, demons run free having very little opposition by the forces of good. Many early episodes deal with various demons and warlocks trying to take over the Underworld and the Charmed Ones facing various demonic factions to prevent the crowning of another Source. Also everytime a new type of good magical creatures are introduced Phoebe is bashed and labbeled as a traitor. Phoebe becomes obsessed with vanquishing demons, feeling guilty by her actions with episodes like Sympathy for the Demon, the Importance of Being Phoebe and Sand Francisco Dreamin' being altered to deal with Phoebe's state of mind.