The fact that they didn't originally intend for chris to be leo and piper's son is obvious just from watching. Chris never acts as though they are anything but a means to fixing his future until the very episode his lineage is revealed. He has no problem with piper dating the fireman before that, does't seem like someone who's life depends on them being together.
Piper and leo's breakup was the sensless thing i ever saw. Watching the show for the first four seasons had me believing their love was destined and strong (This from a guy!), then in 2 episodes...poof! They can't be together because leo is an elder. Then after that he sticks around, making the break up seem even stranger. Let's not forget the fact that just looking at Leo most of the time during this period, you can tell he still loves her deeply (Kudos to both actors, If they can relay all this into even my thick skull, they gotta be good!).
Now, don't get me wrong. The chris storyline COULD have been good with a different execution. Having the son come back into the past to help save his family and future ain't a bad concept. I just think they should have planned it better, so it didn't seem like they were flying by the seat of their pants.
I agree with you about season four, i said the sense
draining in season four. The cole storyline in season 5 left me cold and not liking phoebe much for quite a while. Half evil or no, the baby was still hers, and the casual way she dealt with the babies loss seemed very unlike her.
I think the thing that annoys me most of all is the inconsistancy with no explaination of why it exists. That made noooo sense did it? Lemme give an example. In the episode "I dream of Phoebe" They discover another genii. Now I realize that Shannon Doherty had no intention of returning to the show, and all that, but that fact has no bearing on the continuity of the show. Stating that, the whole time they've got the genii, I'm yelling at the tv "I wish Prue alive!!!". Later in the episode all the charmed ones are "killied", then when the bottle is regained They actually say "I wish the Charmed ones alive." Ok, where's Prue. She IS a charmed one, and the stated wish returned the charmed ones to life. So, where is she?
Btw, it helped alot, and not even close to a waste of my time!
Now i just hafta figure out how to go back in time and vanquish a demon named Brad Kern.