You can play with Sheik all the time just by selecting Zelda and holding the A button at the start of the battle, you don't need to transform into Zelda again, making her independant from the other. With PT you are almost obligated to change of pokemon in order to not get some bad consequences as Sakurai states, making them dependant from the other.
Also Sakurai counts PT has one character profile even though he has three diferent movesets, different from Zamus and Samus, and PT uses the same Final Smash with any of his pokemon which makes them considered as one character.
BTW, I think that if we get another PC of pokemon, without doubt that is going to be Lucario.
Zelda and Sheik are not "separate" as in, you can't get one without the other in melee. You can't select Sheik alone (she is apart of Zelda in the sense that Zelda's Bv changes her into Sheik which is why they are together).
Well we are looking at the site, it was also said that PT is 3 playable pokemon in one by Sakurai (or atleast the skinny white guy that translates his post for us). And it was never stated that you couldn't play as one pokemon all you want. . . just that something happens if you change either too much or not enuff.
" But they also have another stat, which you might call stamina.
If you keep fighting with the same Pokémon, or
if you change them out too often, it’s not so good for the Pokémon.
If you want to be a good Pokémon Trainer, you’ll need to learn these kinds of ins and outs."
We still have no idea what this "stamina" is but it looks to pick up where Zelda went wrong (as in, something actually happens if you abuse the ablity to use different move-sets by either sticking with the cheap one or changing too much). Theres nothing stating you can't be one all the fight, just that rapid changing or no changing has some effect on the pokemon.
Oh, and Zero most likely aint in Samus's profile because she is can only be played after Samus's FS (in which case she actually does appear in the profile). The character "Pokemon Trainer" is completely depindant on these 3 playable pokemon so theres no reason to have 3 profiles for them or 3 FS attacks. They are cleary a team.
As I said before, don't really care about how each of us sees terms like "reps/ slots/ what-makes-a-character" etc here, PT is composed of 3 playable pokemon. Therefore, with Jpuff and Mew2 coming back, you have 6 playable pokemon (and every important role of a series being fulled in the process) in which case I see no need to expect/ demand or even hold hope for any new playable pokemon. (and this is coming from a poke fan
)
Peace