That's more how the writers are now plotting the story than who Ash is traveling with. In addition with the writers plotting the story out more, the animation too keeps improving. May and Dawn only add in the Pokemon Contest journey which further shows off how better the animation has become and also gives the writers the opportunity to include another storyline.

It seems like PUSA entirely forgot about releasing "Arceus and the Jewel of Life" DVD. If you think that maybe contacting Pokemon USA would help, you can do so by clicking HERE.

Science and Nature are looked at to being opposites of each other. One is something humans can control (science) and the other is something humans can't control (nature). Their pros and cons often seem to be opposites of each other as well. Also science is compared with technology while nature is compared with magic which are also both opposites of each other.

I don't think there was any real contrasts between Ho-Oh and Lugia, though it should be noted that long ago Ho-Oh used to roost on the Tin Tower where Pokemon were said to awaken and Lugia used to roost on the Brass Tower where Pokemon were said to rest. Note that "awaken" and "rest" are suppose to be taken as meaning "birth" and "death". Also Lugia is a beast of the sea which creates storms (making it destructive) while Ho-Oh is the beast of the sky which creates rainbows (making it peaceful).

And there are plenty of concepts which Pokemon hasn't explored, some obvious ones is Darkness and Light (though as you said Lugia and Ho-Oh could have possibly filled that one), fact and fiction, metal and stone (though this could be addressed with technology vs. nature), and mind and body.

Well like I said, the only thing that can be done is contacting them through the link I gave. Wasn't there also another season they didn't release?

Those must be the ones I'm thinking of then. So would 4Kids be responsible for releasing those boxsets or PUSA as they now own the rights?

I was just giving opposites, though fantasy and reality is probably the words I was looking for when I said "fact and fiction".

When Pikachu was chosen to be Ash's starter in the anime, this caused the Pikachu species to be flung into being the mascot of the entire Pokemon franchise. So it looks to have become a tradition to release a Pikachu-like Pokemon every Generation, much like how it has become a tradition to have a rodent, bird, and bug Pokemon every generation.

I think if you swap out for a different zone all the blocks you placed on the swapped out zone are removed.

Storyline reason is because Misty is pretty much the only one who takes being a Gym Leader seriously, infact at the end of the Hoenn arc when she went to visit Ash and left the Gym Leader in control of her sisters, apparently a few challengers came by and they just had them to chores around the gym to earn their badges (and at one point they called Misty asking if they could just hand out badges to get some challengers to leave). So yay, unless she can find someone who will take it seriously, Misty is probably going to remain in Cerulean City.

As for actual reason why, it's been said HERE that the writers and animators like swapping out the girl characters pretty much because it's new "eye candy" and girls are much more easier to put new clothing on.