Use ADC to read expression pedal pot, and have config to assign what quantity it adjusts and min/max clamps. Possibility of I2C ADC for platforms that don't have spare pins.
Allow at least two simultaneous BT devices to be connected.
Add support for Midi output, sending Midi PC and CC messages to indicate to receivers the current state. Similar for Bluetooth Peripheral mode.
For platforms that have the available IO, add extra footswitches.