I really like the idea of highlighting these builders because I agree that it's something I look for if I download anything. I'm working on building more again myself but I would consider other playtested/non-CC builds (preferably without needing MOO in my case, but that's not the end of the world).
I've downloaded several great lots but I ran into one very pretty house where I had this issue with builds that clearly weren't playtested. The stove wasn't working and I had to delete a bunch of decor to make it work. There was no functional counter space in the kitchen when I started playing so you couldn't cook at all. The fridge would sometimes have issues with working. The hallways were also way too narrow (meaning only one square in width upstairs. I have it on the recommended lot size and I don't have room to stretch it out there without taking out all of the front yard/garden. It is a beautiful house so I've kept it for now but the family may outgrow it simply due to the way that it was built.
When I've looked recently, I've been unsure about lots I can use other than the ones highlighted by Maxis since those are playtested. Those are great but sometimes you are wanting something different. I'll also say that I don't mind decor but I don't want so much decor that functionality is broken. Anyway, I think it's great to have a thread highlighting these types of builders since that's what I look for as well.
I've added several gorgeous lots - a colonial library, a beautiful floral cafe, an ice-skating rink with a bar that looks like it is from some northern rustic area, a toddler park that I edited to suit my taste, several other specialist builds and several Victorian houses. I've not yet figured out how to build a Victorian and I'd rather download someone's careful handiwork. These all settled in nicely in my game and I appreciate the talent of the people who took the time to build them as well as other lots that might not have been a fit for my game.
I really like that one pretty house I described but if I continue to have issues when I play it again, it may ultimately need to be deleted and replaced. It's an example of the problematic lots that you've described and it made me nervous to download more without knowing if a lot will be functional.
