The Mujaddid vs the Mahdi

An interesting question was raised to me today about knowing who the religious reviver/renewer of the century (the Mujaddid) is or was, as different people have made different claims. First and foremost, the Mujaddid will be a fundamentalist, calling people back to the fundamentals of Islam in their pristine purity, and not an innovator or defender of deviant customs and traditions of a given land. Secondly, unlike the Mahdi, we are not required to know exactly who the Mujaddid is. In the case of the Mahdi, the Prophet (pbuh) gave clear descriptions of his physical features, the name of his father and mother, his tribe, etc. as well as incidents which would accompany his rise to prominance. So, we need to know who he is to be able to follow him in the battle against the forces of evil which will peak with the appearance of the Anti-Christ (Maseeh ad-Dajjaal). On the other hand, the Prophet (pbuh) mentioned in vague terms that at the begining or end of every era/century, Allah would send someone who would revive Islam for the people. This indicates that the religion would virtually die out in different parts of the Muslim world and be brought back to life by individuals chosen by Allah for that job. What this is telling the believers is that true Islam will always prevail, it will never be erased and lost. Because its final form was the last, it had to be preserved as a means of salvation for humankind until the Last Day of this world. The Islam brought by Prophet Jesus (pbuh) was virtually lost within 400-700 years of his departure. 1,400 years have passed since Muhammad’s death and the pure message remains preserved by Muslim scholars and the masses to varying degrees around the Muslim world. So, it is not a problem if scholars differed as to who the Mujaddid of the last century or the one before it was. Some said it was one person, and some said another. As long as the person chosen was not a innovator or a defender of innovation, he could have been the one and it is not important to know who he was. Thirdly, no one can legitimately be declared to be the Mujaddid while he is still alive or before the end of the century/era, as that would imply knowledge of the future, which is known only to Allah.