It's not too late to change these issues from a developmental or engineering standpoint.
The problem, however, is that many people feel these mechanics have been intentionally implemented to foster a certain style of gameplay and to "protect" newer or more casual players.
Are we talking about any mechanics besides the landing lag?
Given the Mario vs. ZSS example, can we still conclude with certainty that it was not intended as a balance mechanic? ZSS is already powerful, as evidenced by the tournament, for various reasons. As a balancing measure because she can jump into the air so often, she might be slow to recover from aerial attacks after landing. As I mentioned earlier, powerful ZSS + powerful down aerial dash + low landing lag would result in a low risk, high reward situation.
Mario may not be as good in the air and mobility departments as ZSS, but perhaps he has little landing lag after certain aerials to make up for it.
Haven't some people in this thread suggested reducing landing lag on certain aerials rather than a blanket landing lag reduction? If so, doesn't that appear to be the exact situation right now with ZSS vs. Mario? Naturally, if so, people probably disagree with WHICH aerials should have low lag, but it does seem that there is variance, as suggested.