Here's my interpretation if the Powerpuff Girls had a Precure season.

"Head commander and leader, Cure Blossom!" (I know there's already a Cure Blossom in HeartCatch but whatever...)

"The pure joy and the laughter, Cure Bubbles!"

"The toughest fighter of the three, Cure Buttercup!"

"And with the power of Chemical X, we are Powerpuff Precure!"

I don't have an origin for how they became Precure yet but I do have a few ideas from a few users in Discord server I'm in. The majority of the PPG villains would be involved. Mojo Jojo, Fuzzy Lumpkins, RowdyRuff Boys, etc.
Princess Morbucks could be a villian to cure. Him would be the endgame villain. Someone got the idea of Him disposing all of the other villains just so he can have his way of taking over Townsville and soon, the whole world. Bunny could be the mascot. Often ditsy but desires to be smarter and become a cure herself, Cure Bunny.

The Powerpuff Girls (C) Craig McCracken

Precure (C) Toei Animation