Hmm a very good question... if Pakistan were secular, it would be like the USA. 100's of races united through patriotism and pursuit of a better life.
Yes, the US has resources to deliver those dreams, so can keep it's citizens loyal and full of hope - but Pakistan has an Islamic spirit in society that maintains that same hope and loyalty without cash.
However, by making Islam more and more politicised and actualised in the state mechanics, the more of this inherent hope you are blasting away. Something akin to 'you should never meet your heroes' - Islam is the hero that gives most Pakistani's hope, but the more you force it - the more failures it is linked to - the less hope it will offer. So keep the beautiful Islam untainted and run your country as men not saints.
As a secular country, Pakistan would prioritise development and progress over morality and dogma. You'd trade openly with the whole world and become a more attractive proposition to outsiders.
You'd have an unrestricted banking system, which would encourage savings and reward it well (with high interest). Therefore, also making people more accountable/taxable for their money.
You would have social laws that would be more progressive but also more clear - i.e. one man, one wife and the law would specify clearly any exceptions. Equal access to resources for ALL religions and minorities but clamping down strictly on hate speeches and hate crime.
The arts would be unfettered and encouraged, you'd also give more power to women - opening up so much of Pakistan's latent talent.
Personal religious values would be heightened as people would seek out religion for spiritual benefit - not monetary or political reasons as it is now.
On the negative side, this does mean selling some of your soul. Compromising some principals - but then who is stopping you from applying those principals in your personal lives?
Yes, Interest would be available.
Yes, you would probably see more women in political society, work and business, perhaps leading to increased 'immorality' but who are we kidding about the way things already are..
Alcohol, gambling, prostitution - all of these things would still be illegal as it is in so many secular countries. A secular country's laws, still must be in step with it's social norms - it is just that the law will be the same for everyone.