This ^^^

They should make all layers in tiers of three. In every furniture option you'll be able to choose the layer tier it goes under. Tier I, is the bottom tier. This is the tier you use for items like the rug so they don't go over the table. Tier II will be used to go over furniture objects in Tier I. Ie. the rug is Tier I, the table is Tier II. Tier III objects, you guessed it, are able to go over Tier II objects. So let's say you bought one of those snazzy crypt candles while they were on sale. You set down your Tier I rug, you place your Tier II table over it, and on top you set your Tier III candle. Now, in order to keep consistent, Tier I objects should be able to go above Tier III objects, because if you're like me and you like to build things, having a cap at Tier III would become a pain in the ass not being able to continue after stacking three pieces of furniture. Also, the object that is on top should always be the one that gets selected first when touched. We've all had that one moment where we had to flip a table over, just to move the object that was on it. I think that about covers my idea on how to make that layering system. Feel free to point out any flaws found within it.