Enquanto eu não descubro outra forma de fazer isso...

syncPost.jquery.js

(function($, window, undefined) {
    var _create_hidden_field, _dump_form_data;
    
    $.syncPost = function(url, data) {
        var form = $('<form></form')
         .attr('method', 'post')
         .attr('action', url);

        _dump_form_data(form, data);

        form
         .appendTo($('body'))
         .submit();
    };

    _create_hidden_field = function(form, key, value, keyModifier) {
        if (typeof keyModifier === 'undefined' || keyModifier === null) {
            keyModifier = function(k) { return k; };
        }

        if ($.isPlainObject(value) || $.isArray(value)) {
            $.each(value, function(v_key, v_value) {
                _create_hidden_field(form, v_key, v_value, function(n_key) {
                    return key + '[' + n_key + ']';
                });
            });

            return;
        }

        $('<input />')
         .attr('type', 'hidden')
         .attr('name', keyModifier(key))
         .attr('value', value)
         .appendTo(form);
    };

    _dump_form_data = function(form, data) {
        $.each(data, function(key, value) {
            _create_hidden_field(form, key, value);
        });
    };

})(jQuery, window);