class Field {
    protected $name;
    protected $value;
}

class DropdownField extends Field {
    protected $options = [];
    // with functions like setOptions(), addOption(), removeOption() etc.
}

namespace Integrations;
class IntegrationsField extends BaseFormField {
    const LAYOUT_POSITION_LEFT  = 'left';
    const LAYOUT_POSITION_RIGHT = 'right';
    protected $layoutPosition = self::LAYOUT_POSITION_LEFT;
}

namespace Integrations;
class IntegrationsDropdownField extends BaseFormDropdownField {}