When my parents built their house in the seventies the disposal switch was right next to the switch for the sink light, next to the sink, but of course when I installed my disposals I put the switch under the sink behind the cabinet door because that's easier to do in most cases. I have no idea what code it....
The only time you should really need an air switch is if you have your hands full or don't want to risk flipping switches with wet hands, which obviously you shouldn't do.
I have a foot operated air switch for a drier next to a tub and I love it. The other end of the air switch plugs into the wall outlet and the drier plugs into that. Pretty slick. And even thought that outlet is on a GFI breaker AND circuit, I feel safer turning on the drier that way.
I honestly don't see the need for one for a disposal, but that's just me
Give us this day our daily bacon.