For those of us who are unaware, the Pakistan movement was a political movement in what was then British India to establish a country for the Muslims that lived there. The movement ultimately resulted in the creation of Pakistan and Bangladesh (the latter seceded from Pakistan 24 years later, which I'll get back to later), and is therefore regarded as being successful as it achieved it's goal of creating a Muslim homeland in British India. This makes Pakistan the only nation-state to ever be founded on the basis of Islam, therefore, as religious Muslims it's clear that we should learn from this movement if we want to unify the Muslim world. There are also things of benefit we can take from Pakistan itself, such as the fact that it has a great deal of ethnic diversity (as a unified Muslim nation would), a powerful military, etc.
However, when one looks at Pakistan itself, we can clearly see plenty of issues with the country. It's not ruled by Sharia, haram acts are rampant throughout society (e.g prostitution, corruption, homosexuality, black magic, music, dancing, interest rates, etc), a large portion of it seceded to become it's own country (Bangladesh), etc. Even the movement itself suffered from issues, such as not having significant support from the Ulema. So clearly, we can also learn from the mistakes of Pakistan and the Pakistan movement so we can make sure a unified Muslim nation can be as efficient as possible, and come about as efficiently as possible too.
Here are some key points on what we can learn:
1. If the Muslim world is to be unified, we have to use diplomacy to do it. We cannot just have one (or a few) Muslim countries decide to conquer the rest, this is unfeasible due to the fact that no Muslim country has the capacity for such a large scale conquest. It's clear that diplomacy can and does work in modern times (to a certain degree, I'll expand on this later) since Pakistan itself came about through diplomatic means.
2. If the Muslim world is to be unified, Muslim countries need to develop a powerful military, no ifs and buts. The Pakistan movement ultimately resulted in Pakistan being much smaller than how it was originally visioned because of the fact that the Muslims of British India lacked any substantial military force to threaten it's enemies if it did not get it's way. Not only that, but if Pakistan did not develop the powerful military that it has post-partition, it would have been destroyed by now due to the numerous attempts of it's enemies to do so (mainly India, but also the USSR and Afghanistan).
3. Most of the Ulema must be on-board for such a unified Muslim country to be formed. If they do not support it, then many Muslims will not support it either and therefore such a country will be difficult to form. We can clearly see this occurred with Pakistan, as many of the Ulema either didn't care about or opposed the movement, weakening it's position among the Muslims of British India. So how do we get the Ulema on board? That brings me to my next point rather neatly:
4. We must emphasise that our unified Muslim nation would be one that strictly adheres to Sharia, rather than loosely associating it with Islamic principles like most of the members of the Pakistan movement did. This would not only gain the support of the Ulema, but also prevent it from falling into the trap of pseudo-secularism like Pakistan did post-partition, due to the lack of a clear-cut vision for how the country was to be ruled.
5. Arabic and English must be implemented as the official languages. English is needed as it is the global lingua franca as well as the most commonly spoken language among Muslims, and Arabic is needed since it is the language of much of Islamic literature (most importantly the Quran). You can clearly see the parallel of this example in Pakistan via it's implementation of both Urdu and English as official languages. However, Pakistan itself fell into a pretty major problem: it chose Urdu. Whilst Urdu was the lingua franca of Muslims across British India (courtesy of the Mughals), it was (and still is) far too similar to Hindi (due to the fact that Hindi is derived from Urdu). This is problematic because it allowed for Indian culture to permeate Pakistan via India's vast entertainment industry, and as a result promote haram acts throughout Pakistan (the saddest part is that Farsi could have been chosen instead, since it was also the lingua franca of Muslims across British India and unlike Urdu, it was much more distinct from Hindi). Therefore, it is also important that Arabic is selected because of the fact that the overwhelming majority of it's speakers are not just Muslim, but many of them are also very strict Muslims, and it is also important that English is limited to being used as an official language only, rather than one used in day-to-day life to ensure that the promotion of haram acts via Hollywood and it's allies is curbed (which Pakistan has managed to somewhat do via a pseudo-implementation of such a strategy). This will allow for Muslims to keep our distinct identity and remain Islamic.
6. A large entertainment industry that abides by Sharia must be promoted within the unified Muslim nation to ensure that, unlike with Pakistan, the members of the country do not look towards foreign media for sources of entertainment and are as a result not influenced by them.
7. The institutions of the country must promote the idea that we are all Muslims and human beings before being anything else, and any ideas (e.g ethno-nationalism) that contradict this must be stigmatised to a great degree. This is in order to ensure that, unlike with Pakistan, a portion of the country doesn't develop a sense of ethnic nationalism that results in them eventually seceding.
8. The unified Muslim nation must become self-sufficient. One can clearly see just how much Pakistan suffered due to sanctions after it's nuclear tests due to the fact that it lacked a sufficient productive capacity. Therefore (just like Pakistan has been doing in recent times), policies must be implemented to promote self-sufficiency.
9. The unified Muslim nation must make alliances, we cannot just be a lone-wolf for the entirety of our existence if we want our nation to remain sustainable in the long-run. Forming alliances would not only limit the number of enemies we have, but also make us much more capable of defending ourselves via the assistance of allies if we ever get into a conflict with our enemies. This policy has been implemented many times by Pakistan (e.g with the US and China), and gave the country access to plenty of weaponry and economic assistance which proved to be helpful. Such alliances are also required in order to make the country eventually become self-sufficient, as it can result in the transfer of the necessary technology and skills for such a capability.
10. The way in which members of the government of the unified Muslim nation must be decided is via Shura. We can clearly see that Pakistan's system of being partially democratic and partially a dictatorship hasn't done the country much good.