First, major props for using the 4 criteria. You'll be more spot on and your roster decisions will make more sense and probably be easier to convey.
#4 is really hard to apply. Most of the time, I kind of just guess because it hard to say what will happen. Just think about what the character can do (#2) and see if that meshes with the rest of the cast.
I think the problem with #4 is that characters are not the same in Smash Bros as they are in their original games.
Take Mewtwo. In the games, Mewtwo's only "weakness" is average defenses, although he is still more resilient than any other Smash pokemon except Lucariom. His attack is high, his special attack is
monstrous, and he's one of the fastest pokes in the game. Logically, Mewtwo would not contribute to the game's balance at all if he was true to his original incarnation. However, Mewtwo turned out to be a low-tier character because his Smash self is lightweight (Even though he's heavy in the games), he lacks psychic powers to murder an opponent from across the battlefield, he's a bit slow, and he has terrible attack power for most of his moves.
Another example is Samus. Samus is
not balanced in Super Metroid; she has tons of health, she's extremely agile, she can jump infinitely while transforming into an invincible buzz-saw, she can lay power bombs that hit everywhere on the screen, she can rapid-fire a wide charge beam that freezes enemies and goes through obstacles, and while her regular missiles do not home, she can rapid-fire them and can carry more than 100. Yet in two of the Smash games Samus has appeared in, she's been low-tier, and she's never been overpowered, and that's because her moveset was severely reduced and downgraded to balance her.
I think it's impossible to predict what effect a character will have on the game's balance. Even something as simple as basic characteristics can fail; yes, a slow heavyweight without super armor (Bowser) is less likely to be good than a fast character with a sword (Metaknight), but characters like Sonic, Pit, and Shiek are not top-tier in Brawl even when their basic concepts seem powerful (Fastest character; a guy with great projectiles, fast moves, and great recovery; an agile character with fast moves and the ability to transform into another character for versatility).
