We are going to approach adding the new rooms (Orokin Lab, Observatory, and Trophy Room) in two phases:
First we need to rush building the Orokin Lab, so we are going to temporarily place it in one of the open nodes in the Grandest Hall. Next we are going to start building the trophy room, which also serves as a Cross Connector for the Orokin Labs and the Observatory:
Second we are going to place two Orokin Labs, in order to build more than 1 towers simultaneously (plus, it keeps the main floor symmetrical about the vertical axis). Finally we are going to place the Observatory, which will serve as the meeting room in a future update:
These are just drafts and are subject to change in the future. In regards to the new garden rooms, we are still in the process of making an appropriate layout since they are much bigger than the current garden tilesets.