Actually its simply genetics. Role models, development and other things play a role, but its defintely mostly genetics.
People always forget this golden rule, Genuine fast pace bowlers are BORN not made.
Its just like sprinters, they are born not made. Sure you can help beef up the pace with training and inspiration, but not beyond a certain point, its minimal really.
Batsmen on the other hand are more or less made. Yes you cannot do half the things brian lara does at the crease without having enourmous amounts of talent, but with hard work, batting can be improved at a much more significant rate than bowling pace.
So pace aside, the reson for which is the genetic make up of most pacemen from Pakistan. Indians have suffered from producing quality swing and seam bowlers due to most of the reasons you guys mentioned.
90% of swing is totally dependant on your bowling action contrary to what most believe. The other 10% is dependent on what you do with your wrist and other skill factors.
I suppose Pakistanis have just been more willing to experiment and develop such skill, this coupled with their pace has made their fast bowlers very lethal.
Indians have produced better batsmen but not more TALENTED ones.
If you look at Inzamam, Yousuf, Saeed anwar and you look at their techniques
they are severely flawed compared to most if not all Indian batsmen with the exception of sehwag.
Inzamam is in a different class all together, he is probably more genuinely god gifted than Tendulkar and Lara, but because he never worked on his game, he will never and rightly not be considered in the same class as Lara and Tendulkar.
I remember when Lara faced Mohammad Zahid who he called the quickeest bowler he has ever faced. Lara could not touch Zahid for the whole over and finally got out to him.
Mohammad Zahid himself in an interview said that one batsmen who he never even remotely troubled in practice no matter how hard he tried was Inzamam. He said Inzamam was never impressed, he would just play me with ease. And this guy was a lot quicker than Akhat at his prime.
Saeed Anwar was a tremendous natural stroke player who always played the same way, but his technique also lacked.
Indian batsmen are just very well groomed, they are well taught and are very hard workers. They are mentally tougher than most Pakistani batsmen in general, and this is why they have consistently produced better batsmen. But I dont think they have produced more naturally talented ones.