First, I have to say I do not smoke anything but if you do it may help with this attempt at an explaination.
The timelines already all exist from the beginning of time till the end of time. So everything that has ever happened or will/could happen already exists in a timeline. So time does not really move we just move along a timeline or path. If something happens on a path we already traveled, it would throw us onto a different path. So when Billie and Christy stole Wyatt's power, the future Wyatt and Chris jumped to a different timeline. Being supernatural they realized this so to get back to their preferred timeline, they had to go back and correct the thing that made them jump to the alternate "bad" timeline.
I am still trying to figure out how to go back and correct the incident that threw us into this "bad" timeline and get us onto the one where Brad Kern was fired after season 4 and Constance was brought back and she hired better writers and Shannon came back to the show for many guest appearances each year.
I understood your explanation just fine the first time. I never thought of it that way though.There's one thing that doesn't completely make sense about your explanation. Maybe I'm just not understanding it completely, but how would Wyatt & Chris notice that they've jumped into another timeline? It's fine if, you know, they were fighting and suddenly they were in another place or something. But the only thing that happened was that Wyatt lost his powers. How would they immediately know that it has something to do with what happened about 20 or so years ago? Are we to assume that magic has advanced over the years or something? Or that they have some sort of ESP?
Also, in past episodes we've noted how the sisters are always told not to mess with the past because it can screw up timelines. For example, in "That 70's Episode", Phoebe changes her mind at the last minute and removes the note that could save her mother's life from the Book of Shadows. Had Patty seen the note and the future changed, I highly doubt that future Phoebe, Piper and Prue would've noticed any difference simply because they are supernatural. They wouldn't know anything else so life with their mother still alive would've been normal to them. So, if baby Wyatt's powers were never returned, he would've grown up without any powers. Thus, his adult self would not notice anything different. And therefore, the boys wouldn't have returned in FC
I completely understand what you're saying about timelines existing from the beginning of time and all, I just don't see how any being, supernatural or otherwise, could realise they've jumped timelines. And nor do I think that your theory fits in with what we've seen in previous Charmed episodes.