“Why do we need to identify the “absolutes” of the Shari’ah as a basic step in formulating the parameters of an Islamist political platform; why could we not just form madhhab-based parties? ”
Well, frankly, it is kind of embarrassing that we don’t all already know the absolutes. It is embarrassing that, as an Ummah, we don’t know what from our laws is from Revelation, and what is from interpretation. We don’t know what is fixed and what is flexible. What is non-negotiable, and what is open to discussion and debate. Of course we should know that, just as individuals. But for the purposes of Political Islam, I think it is essential. An Islamist party platform needs to comply with the agreed upon rulings related to the public sphere, or else, how exactly would it be Islamic?
You don’t really want a party to base its platform on a particular madhhab because you can’t impose the interpretation of your maddhab on others. That would legally invalidate differences of opinion which are perfectly permissible. I don’t think that an Islamist political party should dictate interpretation, but it should uphold what is explicitly legislated and agreed upon.