Guest vLAN through AP connected to a remote switch?

Hello! I am on an Asus N66U with Shibby's Tomato Firmware 1.28.0000 MIPSR2-123 K26 USB AIO-64K. My house's walls are made out of solid concrete which is terrible for RF. To compensate, I am physically configured with the N66U router on the 2nd floor connected to an switch and all the ports on both the switch and the Asus go to more switches in rooms or open areas of the house, and those in turn to mostly appliances like TVs, STBs, IP cams, etc.

One place it goes I would like to run a guest...

Guest vLAN through AP connected to a remote switch?