Friday as holiday
The fundamental reasoning behind the Christian day of rest is the belief that Almighty God Himself rested on the seventh day, after "labouring to create the world for the previous six". Of course, it is anathema in Muslim belief to think that the Almighty has any 'needs', let alone a need to 'rest'. Hence, it is no surprise that during the time of the Prophet of Islam and the subsequent righteous caliphs, business went on as usual during Fridays on the bustling market-places of Medina, Damascus, and Baghdad. Indeed there was a proper break of trade during the congregational Juma prayers, just as there was a short break for each of the other five canonical prayers. The Holy Koran is very clear on the matter: it asks believers to suspend trading once azaan is called and then go back to their business after namaaz is done. The idea of having entire Friday off on the premise of Juma prayers is not only absurd, but possibly an un-Islamic innovation of practices blindly imitated from colonialist Christians.
If there has to be a day off, it should be the day that does the least damage to the economy of the country and the well-being of its inhabitants: not only does Islam allow for this but probably, as a religion which places such a high premium on business and trade, mandates it.