I have worked on prototype which uses GSM module to accept commands via sms text, Voice recognition module for speech dependent commands, touch screen for menus, keypad, info. All modules communicate via serial ports. Atmega 328P was more than enough. You can use I2C port with MCP23017 chip (upto 8 chip can br used) for port expansion (8x16) ports.
With this and software serials, you can have a head module communicate with upto 5 serial port modules and 128 switches. One serial module can be another Atmega 328P which can handle other expensive tasks (multi core architecture)
I can help you with prototype and coding.