perhaps use multiple nanos and communicate over serial to central?
More processors is usually a beginner's mistake.Port expanders is usually the better solution.16 analogue channels per analogue pin with this board.Leo..
Just to emphasise Wawa's pointNo, never do this.
Communication and synchronization between multiple processors is hell. Having to maintain two different programs is cumbersome. Microcontrollers are more expensive than multiplexers.Using a multiplexer requires 10 lines of code, communicating between multiple processors is much harder.Pieter
Altho OP is probably well below the hard stuff