Botler 1 will have different subsystems that will have to communicate. A Raspberry Pi is required for the webserver part of the system. It will manage the buttons pressed by the user and the camera streaming.
Other subsystems will use the cheaper Arduino.
I was thinking about using microcontrollers from Microchip but it could cost more, it would be a longer development time and it would require PCB boards ad hoc.
What about the communication line for the hardware? CAN-BUS modules are available and compatible for the two systems.