I think if a cheat like that existed it would break the save if used too much.
Hence why they haven't added open world because they have to remodel all worlds and break all saved games in the process.
If I'm correct, and correct me if i'm incorrect. In game codes Sims are like magnets. They're linked to many different objects in order to use them and perform multitasks with it smoothly. The codes of sims scan every item like 1000 times a second. This is also why your game lags like crazy if you have a ton of items in your houses and inventories because the scans are trying to keep up, draining your RAM.
Now they're linked to all the objects that can be used in the neighborhood, if open world is suddenly added, or many items are suddenly removed, the scans would overload resulting in a game crash, or broken game save.
I'm not a game developer or anything, I just quote what I read once earlier and made the most sense to me.