EA has provided ways to place objects anywhere on a grid, but many objects have no way to move them up and down. This should be fairly simple to accomplish by just modifying the appropriate Z values inside of the lot package.

I just did this manually using SimPE to make a hotel sign out of the (hidden) luggage object and it was pretty simple, although I need to do more testing on it before I can say for sure that it works.

More info:
Objects (including animated objects) remain in the new location; however, when installing a new EP, the auto-reset of the lot can cause the objects to return to their original location. It's just as easy to fix in Apartment Life as in the base game, but shared lots may need to be fixed. Too bad.

Still, I like the effect in my neighborhood.

Interesting. Are there BHAV instructions that can affect this value?

I don't know. I'm not very familiar with modding in-game behaviors.