Regarding the Fighter Pass pricing, it is in line with the season passes of other fighting games, so it is among its peers.
If you reject the concept or feel that such passes for fighting games are too expensive on its own, then fair enough.
One of the 5 characters has to be Rex/Pyra due to the popularity of Xenoblade 2, right?
I hardly consider that fair--Mewtwo wasn't preorder exclusive and could still be bought separately.
I was under the impression that Piranha Plant is free as a pre-order bonus and paid later, like Mewtwo.
Read the article--that's certainly not how the info is worded. Everything so I've seen so far only seems to indicate its availability only as a time-limited bonus. Unless you have data suggesting otherwise, I'm going to have to assume your impression probably came from wishful thinking.
I'm pretty sure Piranha Plant will function as Mewtwo did. Granted, Nintendo does some bone-headed stuff constantly and consistently, but I don't think they would do that with Smash.