Two are immediately occupied in each room: one by the "wireless bridge" (Wifi router, Zigbee gateway
Wait..what??! Dear God no! Please tell me you're not NATing your primary network into different networks for each room. That's a very bad idea, especially when you're in a home network environment with shared multi-media resources such as music and movies.
You only have one gateway/router device in the home. It, in addition to your ISP modem, would be located in the same room as to where your CAT6 patch panel (where all the cables converge in one area) would be. Newer homes actually have cable distribution panel built into the wall of someone's closet. During the build out, fiber or coax would also be ran to it for the ISP equipment. Do keep in mind that 16 port switches and above can get to 1U rack mount form-factor sizes; so plan on the size of the distribution panel in advance or else that will be mounted on a ply baseboard like some telco closet (unsightly IMHO).