From the Backbone Validation documentation:
// validation attribute can also be defined as a function returning a hash
var SomeModel = Backbone.Model.extend({
  validation: function() {
    return {
      name: {
        required: true
      }
    }
  }
});
You could then adjust your model to have a function:
var SomeModel = Backbone.Model.extend({
    /**
     * List of field which are required.
     * @type {Array|Function}
     */
    required: ['firstInput', 'secondInput', /*...*/ 'tenthInput'],
    /**
     * Same format as Backbone Validation
     * @type {Object|Function}
     */
    specificValidation: {
        firstInput: {
            pattern: "email",
            msg: 'Email!!!'
        }
    },
    validation: function() {
        var inputs = _.result(this, 'required'),
            rules = _.result(this, 'specificValidation'),
            requiredRule = { required: true, msg: 'Empty!' };
        // apply the default validation to each listed field
        // only if not already defined.
        _.each(inputs, function(field) {
            rules[field] = _.defaults({}, rules[field], requiredRule);
        });
        return rules;
    }
});