Answered by Shaykh Faraz Rabbani
The issue is that when a muqalid follows the opinion of his own madhab, in a single issue he is not allowed to follow another madhab in the same issues regardless of the fact that he performed the actions competently from the other madhab. i.e. the Hanafi is not allowed to follow the Shafi`i in salat say (assuming he repeats his wudu, because this is the condition required to accomplish the salat). Because the muqalid is convinced – for the action he has already performed – that the opinion he follows is the Hukum of Allah for him and that all other opinions are not the Hukum of Allah on this issue – regardless of the fact we respect all of the Imam’s of the Madhabs, and that they are all valid Islamic legal opinions. There are conditions when he can change the opinion he follows in a matter which he has already practiced, and these are based on knowledge of the hukum, trust of the opinions of the madhab he follows, unity of the Muslims, and obedience to the Ameer, and not related to durura (hardship) as this will make him judge according to his nufs not the hokum Sahri.
The point I am trying to stress is that the Muqalid does not have the capability to outweigh legal opinions. This will make a mockery of the deen. To give the examples when it rains the Hanafi may say – because it is raining today I will follow Shafi and join my salat as a resident. Or the woman could extend/ shorten her hadth from 10 to 15 days. Or the male Haji can only accomplish his tawaf and Sai as Hanafi as he may break his wudu – by touching the women, according to the other madhabs