implemented in the first place?
Your looking at this from the wrong angle, my friend. The British colony was made up of various
provinces. These were mostly centred around a ethnic group - although it was not quite perfect. Here below is map of these provinces. In the west Baluchistan, Sindh, Punjab, NWFP and Kashmir were Muslim majority. It was these that voted to join the federation called Pakistan. They had anything between 70-90 per cent Muslim majorities.
On the map you posted (bottom of the page) I have drawn a saffron circle - that centres on the
Ganges River Basin in India. This
core region of India and is densely packed. It probably has about 600 million people living within it. Although the number of Muslims could be as high as 60 million in the
Ganga River Basin but they are dwarfed by the 540 million Hindus. Futher most of the Muslims are indigenous to the ethnic groups there - that means they are more similar to their neighbours then those Muslims in the far West of what is now Pakistan, which of course is dominated by
Punjabi, Pashtun, Baloch, Sindhi ethnic groups. All of these groups that make Pakistan are located inside the green rectangle - which is centred over the
Indus River basin.
Kashmir also falls inside the green rectangle but as you know that is where the dispute is.
And your idea would never have worked. As the example of Bangladesh showed in 1971 war it is better to have more compact, cohesive, integrated and geographically contigous country then one that is huge but spread over vareigated regions and ethnic groups held together just with a loose notion of Islam.
I hope this helps.