Positives: - Economic boon as labour costs are reduced - Concubinage of captured women would remove the perversity that has affected our society i.e. large pornogrpahy use, teasing of women in public quarters, sexual perversity as evidenced on youtube videos of young pakistanis. With concubinage young muslim men have a healthy outlet to engage in before and after marriage. - Reintroduction of our practices and removal of western secular concepts that are based around the French revolution. This would remove the ideological confusion many of our less intelligent muslims face i.e do we support the French revolution or Islam?
Cons: - Could lead to slave rebellions like the Zanj revolt but this could be easily avoided in my mind.
Without addressing the moral issues:
-It would not help economically, as Islamically a slave's owner is obliged to feed and shelter his slave at the same standard as himself. This means the economic cost of emplyment would rise. If you are wealthier in Pakistan or most Muslim societies, you can exploit poor labourers by payng them poverty wages. such that they can barely afford food if they are lucky and completely inadequate shelter. Having to provide food and shelter for them at the standard required by Islam would in fact be more expensive.
Secondly, in an environment where people no longer being slaves, what do you do if a slave refuses to accept it, and refuses to work. You are not allowed to beat slaves, and yet you still have to look after their welfare. Unwilling slaves would end up being an economic burden unless freed.
Iran and Mutah marriages show that even where the population believes that there is an islamically valid way to access easy sex, perversions continue. Therefore you can discount the role concubines would play.
Looking at the life of the Prophet (pbuh), by the time of his last major conquest (Mecca), he stopped taking slaves even in war. That, coupled with the strict rules about slave welfare that I mentioned above (no beating, no exploitation), suggest to me that like divorce, Islam permits yet frowns upon slavery.