This is more an argument against your own point. Some characters ARE indeed tournament viable and would be excluded from your tiers because there's a few characters that get in there before them. Like, it makes no sense to have DDD be a mid tier as part of the numbers and Doc as a low tier right next to him if their actual viability is about even, y'know? :/
Gaps appear more illusional in this game but only at first glance. You're still going to see these characters
winning tournaments far more than the likes of
etc, or even more than say
and so on. I think there should definitely be gaps to separate that instead of arbitrary rules. As I mentioned previously, if we use your system, what's the difference between what you're suggesting and just doing an ordered list from first to last? Arbitrary tiering is totally useless, you don't argue a character is top tier because they're 'top 6', you argue they're top tier because their results are near the same level of those already IN the top 6 - or in other words, instead of having a top 6, we would now have a top 7. That's why these discussions are important.
And yeah, ZSS and Rosaluma do have bad MUs, but how positive and negative MUs affect your tier position is relative to the game, the rest of the cast. That doesn't mean they don't win far more than the lower tiers.
I don't see how relying on a decent kill throw is a bad thing. Two characters in this game have kill throws as their crux move, and at least 5 more have them as supplementary kill moves should the opponent live too long. Those things are legit man. (sorry though, don't mean to attack everything you're saying, just wondering how you come to this conclusion) :3