Other things I'd like:
-Curved fences are amazing! In the future, it might be nice to be able to exploit both sides of the curved fence (the concave and convex sides). I'm attaching two photos as an example where I was trying to create a reverse curved railing on an upper floor, but I couldn't delete the floor without deleting the railing. And there were gaps in the floor on the opposite side of the railing. I hope my photos show better what I'm talking about.
http://i1129.photobucket.com/albums/m502/billsimnyc/Anse%20Chastanet/ReverseCurveFence2_zps0f32cf60.png
http://i1129.photobucket.com/albums/m502/billsimnyc/Anse%20Chastanet/ReverseCurveFence1_zps487af5e6.png
-Ceiling beams and rafters would be neat--especially if we could draw them like fences and criss-cross them to make coffered ceilings
-Low fences that Sims can step over. Would be nice to zone rooms and gardens and still allow the Sim to route through them.
-If octagonal and conical roofs return, which I hope they will, please make sure they cut away the lower roof sections appropriately--this was always a problem for me in TS3 when you could see the roof on the inside of the house through windows if there was an octagonal or conical roof above.
-Like you said, please allow collectibles and Sim-crafted items like paintings and sculptures to transfer. These add so much personality and individuality to a home and were so much fun to share in TS3--like unique nectar recipes, artifact collections, inventions, etc.
-Allow upgraded appliances to transfer as they did in TS3. I thought this also added character, depth, and detail to our builds.
-Allow ceiling light and decor heights to be adjusted, perhaps by dragging the mouse up and down or with the arrow keys, so that the suspending chain for a chandelier, for example, would lengthen and make the light hang at a more reasonable level. This is important in the taller rooms where those lights look silly suspended so high on the ceiling.
-I don't know if I have a glitch, but when I rotate my lot, the landscaping/terrain painting doesn't rotate with it. This is kind of difficult if you need to change the orientation of a building on a completely different lot, but the landscaping stays fixed.
-Ability to delete flooring sections without deleting the entire room's floor. I've had problems where I try to do this by adding a small room the size I want to delete, then deleting the floor and walls of that room, but the floor will pop back into place. Or if I somehow get it to work, the edge of the deleted floor section is still visible, floating in air.
-Variable tree and bush sizes would be nice with each subsequent placement like we had in TS3. I know we can magnify with Shift + ], but that is sometimes way too dramatic. Subtle differences in the plant sizes would make things more visually appealing.
-Gallery links or codes would be incredibly helpful for creators to share their work more easily. I know that the Gallery no longer works through an independent website, so I thought codes might be a useful alternative to website links. For instance, I could post on my blog or Facebook that I just shared a lot on the Gallery, and my friends would be able to find it by typing in a given unique code for the lot once they are in the Gallery. I worry that a lot of creations are getting buried in the heap because there is otherwise no way for creators to link directly to a lot or household they've spend a lot of time and effort creating. And as our catalogs continue to grow, it won't be sufficient to just have people look up our account to find our build because it might still be hard to find amongst our many other creations.
-It might be nice to be able to choose from different camera shots when uploading a lot to the Gallery, just as we are able to do with our households and rooms. The automatically generated camera shot is sometimes not so flattering, particularly for houses built at an angle on the lot, and it might be nice to be able to choose from different perspectives to best show off our work.
-Object fading is nice for gameplay but really bad for photography and moviemaking. For example, I use camera mode a lot when I take photos for SF Magazine or videos of my lots for YouTube. Right now, things like trees, bushes, columns, and ceiling lights fade and disappear when the camera gets close to them. I can see why that would be useful during gameplay mode, but it's nice to be able to see everything in the camera shot when we're in camera mode without having it disappear. The only way around it right now is to take shots in build mode, but that doesn't allow for the sophisticated camera movements, zooming, and positioning in camera mode.
-It would be nice to turn off the blurring of distant objects in camera mode (like turning off aperture priority or making the focal distance infinite on a real camera). This makes capturing long distance views of our lots very difficult as they are often too blurry from far away, but zooming in to get in focus prevents us from capturing the entirety of the building or shot we want.
-I echo your request for buydebug invisible lights, mailboxes, and fog emitters!
Gameplay issues relevant to builders
-It would be nice to be able to sell everything in the family inventory with the click of one button instead of selling off each individual item one by one.
-Reading books is always a great way for Sims to improve their skills. However, there's an issue when the Sim goes to work or off the lot for any reason and places the book in very random locations instead of putting it in his/her inventory or on the bookshelf. That leaves the player searching all over the place for that book to continue reading after the Sim returns home.
-The cheat options to fill Sim or household needs and disable need degeneration are great for builders, photographers, and movie makers. I've noticed that those cheats need to be continually reactivated, though, when Sims return home from work or go off of the lot. It would be nice for the game to recognize that those cheats are still active no matter where the Sim or household is located.
Other
-You mentioned that fences snap up to the foundation level, but I found that it depends on which direction you draw the fence. If you start at the foundation, a foundation level is added to the bottom of the fence, but if you start away from the foundation and draw towards the foundation, the fence will stay on the ground as you can see in this photo where the hedge fence stays on the ground as it connects to the foundation.
http://i1129.photobucket.com/albums/m502/billsimnyc/ashford/Ashford2_zpse139afd2.png