I disagree with any of these ideas, except possibly the Third (that is, if it's tweeked a little).
A Pokemon evolving four times would go against the established rules set so far. And when I say evolving four times, I mean having four stages, not having three stages and then an alternate for the last one. No, I mean the "I'll evolve four times and have uberly stupid stats" kind. That's a big No-No and is quite boring.
A Normal Pokemon evolving into any type it wants would mean about 17 useless Pokemon from that single Pokey alone. That's a waste of space that could be put to better use by other Pokemon--dual types especially. Besides, part of the fun in raising Pokemon is not knowing what you'll get next.
I would only agree with the last one if A) the new, weaker evolution got a special move or ability to compensate for its weakness (ala Shedinja), or B) If the weaker portion of the new evolution was allocated to fewer moves, bad ability, or things of that nature--NOT stats.