sipahiro Have you guys ever played Homescapes?
Never played it, but with isometric, so with both fixed camera and objects that are aligned to a grid (perhaps able to rotate but only through 90°) everything can be pre-rendered. 3D elements can be added, and sorted to put them at the correct depth – you need z-data to sort the isometric elements which makes it easy to include 3D objects, as long as they align to the grid too.
At least that’s what it looks like in that screenshot. It’s how many other 3D games have worked down the years, including many Flash games.