changing symbol option only in MapQuest/Leaflet

Question

Using MapQuest, I want to create a flag with the same colour/size options, but different texts (symbol option) for different locations.

In the js function I have:

var iconA = L.mapquest.icons.flag( {
     primaryColor: '#2240fF',
     secondaryColor: '#ff5998',
     shadow: true,
     size: 'sm',
     symbol: 'K1'
}) ;

I want to be able to override symbol with 'K2', 'K3' etc, but keep the other marker options.

What I would like to do is to create a loop as follows (assuming the data object has been correctly instantiated):

for ( i = 0; i <= data.length; i++ ) {
   var iconI = iconA.include({ symbol: 'K' + i });
   L.marker([ data[i].lng, data[i].lat ], {icon: iconI} ).addTo(map);
}

This does not seem to work, even though that seems to be what the Leaflet documentation on extending classes implies.

A way that works is:

for ( i = 0; i <= data.length; i++ ) {
   var iconI = L.mapquest.icons.flag( {
     primaryColor: '#2240fF',
     secondaryColor: '#ff5998',
     shadow: true,
     size: 'sm',
     symbol: 'K' + i
   });
   L.marker([ data[i].lng, data[i].lat ], {icon: iconI} ).addTo(map);
}