Ok, then I think we're just working off of a difference in terms. When I'm saying "forcing character imbalance", I mean in relation to natural balance, in which case everything we do alters natural balance in some way. What I'm implying... well, that's not really true, because I'm saying it's a fact, is that changing the legal stage list from anything to anything else will alter natural character balance, so when we do it, it must be done judiciously.
I think this thread has adequately proven that hazards alter the competitive scope of the game, that's true. Whether they are clearly anti-competitive is a very blurry distinction, and I think that's still being figured out a bit. Either way, Brawl's nature as a non-traditional fighter means that we can't judge it's merits, as well as its component parts, by the standard rubric that we'd apply to other games. For instance, part of the reason that we equate "non-player based damage" to "bad damage" (for lack of a better term) is because in Brawl, we have had to, for the sake of argument and having defined terms, treat % damage in the same manner we would treat damage to a health bar in any other fighter, but that's not really accurate, is it?
I mean, let's examine the finite differences. In a traditional fighter, health directly correlates to your life; there is a numerical value to the amount of damage you can take before you lose. Also, health is lost even during shielding; you can sit in a corner and block all day, but you'll still take chip damage, which brings you directly closer to death.
However, % damage in Brawl doesn't operate that way. The proof is that there is no finite amount of damage you take before death. You may die at 100%, you may die at 150%. Hell, you may just be able to survive until 200%. Or, you could die at 5%! So, unlike damage in a traditional fighter, damage in Brawl has a correlation to death, but is not a causation! The actual cause of death is KB, not damage; damage is only a gauge of how much KB you might get from an attack. In fact, in Lucario's case, damage isn't even objectively negative! In his case, damage management is MORE IMPORTANT that damage mitigation, as the opposite is the case with every other character.
Again, the question to ask when dealing with how "competitive" something is is really a question of practical options, a question of validity of choice. In Lucario's case, taking damage is a valid option towards performing the task of getting the KO. In any other character's case, we have to determine whether utilizing damaging hazards is a valid option towards getting a KO. We've proven that it isn't always even, in that sometimes hazards do not affect players evenly (such as Halberd's lock-ons). Sometimes, they do (such as in the case of transforms and general space hazards, such as lava or acid). We have yet to accurately determine whether using generally non-random, non-partisan hazards to secure a KO is a competitively valid choice to make, which is different than if it is a FAIR choice.
After all, if we're in the game of determining what is fair or not, and only allowing "fair" events to happen, then we have to only allow dittos, because it's not "fair" that different characters are inherently inferior to others (note: player choice is irrelevant here, just like we're assuming it is in stage selection; if a player isn't free, without a ruleset exception, to make a choice of WHERE to battle, he shouldn't be free to make the choice WITH WHOM to battle, either). Of course, it's implied that this only applies to changes made for non-warranted reasons (saying it isn't fair to circle-camp is different that saying it isn't fair to plank; one destroys the game outright, the other is just annoying).