Could a robot have a mini-robot attached to it by vex string, wired to the microcontroler on the main robot. The mini robot can fit on the main robot within 18 x 18 x 18, and is controlled by a partner joystick. the mini-robot doesn’t have any microcontroler or “brain” of any kind on it, and remains connected to the main bot.
Would this be legal?
Yes, this is legal. However, please be mindful of <R3c>, and the definition of Entanglement. Any sort of “tether” device will undergo extra scrutiny in regards to this rule. If your tether consists solely of flexible items such as rope or PWM cables, it would violate <R3c> as an unnecessary risk of entanglement. You’ll need to back the tether with rigid structural material to avoid violating <R3c>.