Please not the if we are using a code, we should strictly adhere to all the provisions and stipulations of the code. Just in case of WSM, we can not use any kind arbitrary load factors. We must use unfactored load combinations. It is our duty to use software correctly following the codal provisions in the stipulated manner. If you are using LSM method, you can use factored load combination. In LSM method you can use reduced load factors to consider this provision. There was a similar type of discussion on steel structure in a different forum. You may refer to that.
www.sefindia.org/.../viewtopic.php
Please note that if you are performing a design using a new process which is not recognised by the code and practicing engineers, the design would not be approved by the approving authority.