Hide 'readOnly' property for my custom class - use Components

[Ticket cloned from T2383: Removing properties for questions created by custom toolbox item]

Hi,

I want to hide 'readOnly' property to my custom Item.

My toolbox item:

JavaScript
creator.toolbox.addItem({
        name: "clientinfofield",
        isCopied: true,
        iconName: "icon-default",
        title: "Información del Cliente",
        json: {
            'type': "text",
            'customType': 'clientinfofield',
            optionsCaption: "Select a country...",
            readOnly: true,
            showReadOnly: false,
            choices: [
                {
                    value: "clientRef",
                    text: "Client REF"
                }
            ]
        }
    });

I'm trying with these options, but don't work:
1.Survey.Serializer.addProperty("clientinfofield", {name: "readOnly", visible: false});
2.If you see, I added a custom property in json object 'customType', to try get it here and hide the property:

JavaScript
formCreator
        .onShowingProperty
        .add(function (sender, options) {
            if (options.obj.customType == "clientinfofield" && options.property.name == "readOnly") {
                options.canShow = false;
            }
        });

any idea?, or can I not allow to user change that property for my custom toolbox item?.