I'd love this option too. I hoped for it when DHD was released, I know others did too. When the decor to the max kit was released I heard more hopes for it from other players but knew it was a stretch.
It's an intense source of rage for me that adding the option to create more colours and creative flexibility in CAS just broke it and created the random makeup bug instead! I miss MAC makeup!
So I see how in practice adding these things on even just one part of the game can cause issues.
I like houses to look different though and in Sims 3 pets in particular I loved the ability to use any colour or pattern on anything. If I had Sims without much money I'd create Burberry, Gucci or L Vuitton patterns for them and their furniture so they looked minted anyway!
What I would quite like is for styles that have been used in Build Mode to be greyed out to show you had already used it on another build. So houses don't end up looking the same because you've absent mindedly used the same colour scheme twice. Still useable if you wanted to, but just an indicator to remind you that you'd used it already. I'm in build mode sometimes thinking does somebody else already have this style? Did I use these colours last year? If it was greyed out or highlighted to tell me I'd used it already maybe, or a little number in the corner of how many times I'd used it. Same with clothes as I tend to give each Sim their own colour scheme to avoid duplicating outfits and having an embarrassing moment when 2 Sims arrive in the same top! You change your top, no you change your top!