Kitchen Wiring 14 to 12 Neutral
Switches are not circuit breakers (overcurrent protection). They cannot protect wire and do not make it ok to use smaller wire past them.  

If any 14AWG wire is used, you must downgrade the breaker to 15A, and downgrade the countertop receptacles to 15A. The other wire can remain 12AWG.  This will mean it is not one of the two mandatory 20A circuits for countertop receptacles and you may need to add a circuit.   

There is another reason not to put kitchen lights on receptacle circuits. An appliance trip will plunge the cook into darkness.