Monstrata, I'd argue that natural things are rarely perfectly straight, or maybe I should have used the term "organic" instead, but this is kinda beyond the point. Also my motivation for making this proposal was because of how easily aesthetics can be overlooked, and not because squartatrice is a terrible map or I'm afraid to hurt soulfear's feelings. There wouldn't be much to mod anyway since everything has already been pointed out by others and denied.
Reading some other comments, I realize some terms should be defined here: "aesthetic" and "visuals" should not be confused with "beauty", it's about intent and care in design, and not about enforcing some kind of defined style.
My intent is to improve quality in general; Osu being a visual game, it seems pretty obvious that visuals should play an important part in the overall quality of a map, though since it's still a game first and foremost, gameplay should be the principal objective, so I can understand the leniency here.
There's also the issue of sameness and yes, more diversity is needed, but surely not at the price of reducing the quality. If the community overwhelmingly agrees that a map can be improved, even if the mapper disagrees, why should it be ranked? What's the point of a design that only the mapper himself can understand especially in the context of a ranked map? That's also where I believe the line should be drawn, between understanding and agreeing.
Taking Monstrata's A.L.I.E.N for instance, I'm pretty sure the community understood the design choices of the map, but not everyone agreed with it. As long as we can make sense of it, it should be allowed.
But yeah, in the end, it kinda comes back to what we already have, so this is probably not a guideline that we need or it'll have to be very long and specific.
I'm not really sure what would be appropriate then, but I still believe this is an important topic so I'll try to work out a solution eventually, it just won't be via the RC.
I think the thread can be closed here unless people still want to debate this further or have some better ideas.