If they replaced the "colored" sets with the abilty to PAINT the furniture, that would be FINE BY ME.
That would be great. Maybe you could bring any furniture into Tom Nook and pay a fee to edit it, by choosing an overall color or maybe even placing your own patterns on furniture. Of course, this would probably have to have the same effect on furniture as it does with patterns -- placing it in your house wouldn't count as part of a set. Because then you could have the entire modern set, but half of it's painted neon green and the other half magenta and that just...clashes, so that'd defeat the purpose of the sets.
To paint...
Maybe they could give you the option to put more than one pattern up on the wall. Like, you could make a mural.
That would be cool.
That would be great. It'd be really nice if you could place patterns on both the wall and the floor like you can on the ground outside -- selectively.
I'd also like to see an option to cover your entire town with a single pattern. It takes waaay too long to do that if you try to make your town a water town, or a lava town, or something like that. If you want to stop it right before the ocean, have stepping stones, whatever, in your town you'll have to do that separately, but it'd take longer to remove + replace than cover 90% of the town in the first place.
One more thing; I really think the design editing needs to be completely redesigned.
Colors: You need to either be able to use all of the pallettes in one design (so it displays only a few colors on the screen at a time, but when you switch to the next pattern to see the colors there the colors you already have down won't change) or just give you all of the colors at once. You can hardly do anything with the meager color selection in place now.
Viewing: You need to be able to test out your pattern while you're making it. Put it on your clothes, spread it across the floor or walls, or make it an umbrella. Otherwise you may finish it and you'll have paid the 350 Bells for it and have to go back and edit it for another 350 Bells.
Storage: You need to have more space for designs, and there should be a way to access designs by people which are not on display. I can't recall exactly, but I believe there was a way to store designs that you weren't carrying in the original Animal Crossing. No such system exists in Wild World, so you have to create multiple characters to get all of the designs stored, and then after not playing it for a while you have to go in and check to find the person with the design you want. Once you finish a design, it should ask you if you want to make the design public or not. If it's public, it goes into an album or something that everyone can access and take designs from. If not, only the creator may access it (unless they put it on display in the shop). The point of the designs put up for display would be that those are the only ones that animals can wear.
I doubt the accessibility part will be done, but hey, I can wish, can't I?