Volker Nienhaus made some interesting points, which I think could form the basis of a very interesting paper, which I would like for you think about.
1: Islamic Banks were founded on the premise that Islamic Economic system provides social justice not available in capitalism. This is clearly stated by Mufti Shafi in his booklet on interest, as well as Maudoodi and many others.
2: Initially, founders had to make many compromises, so they could not deliver on these promises, but argued that they would evolve in that directions (the famous Musharka of Taqi Usmani -- which he thinks would lead to social justice).
3: The movement in Islamic banking from its starting point HAS NOT BEEN towards greater social justice, but rather in the opposite direction, towards greater accomodation for capitalism -- many evidences can be provided but one is the huge participation and DOMINANCE of Western banks in the Islamic finance movement. Whatever their motives, it is clear that providing social justice Muslim countries is NOT one of them.
4: Islamic Scholars/Shariah Boards have been part of the problem, not part of the solution. -- They have found clever ways to circumvent the spirit of Islamic Laws while following the form. Again, huge amount of evidence can be provided on this issue.
5: The move towards the social justice of Islam will require a broader vision, than shariah tricks to make permissible conventional western banking. So far IGNORANCE of scholars about ECONOMICS has prevented this -- Rudimentary economic knowledge of scholars has been a source of the problem. For example the Al-Azhar fatwa of permissibility of interest was BECAUSE the Sheikh was convinced that interest was necessary for operation of modern economy. Similarly,I think Maulan Taqi Usmani's failure to understand economics in sufficient depth has led to many mistakes by him. Nienhaus thinks the solution is to get economists on board with Shariah scholars, but I am not sure this is true.