Air shows are exactly like car shows. You invite your prospective customers and the companies who intend to sell their products in your market. Now lets see how these 3 countries fit the bill.
China: Could be a potential seller, but not possible due to strategic reasons.
Pakistan: Could be a potential buyer, but haha as if thats ever going to happen. As far as selling their products is concerned, what does Pakistan have to offer which is not Chinese essentially. Invite China instead, inviting Pakistan will be redundant. And yes also the strategic factor.
Iran: Potential Buyer, but India cannot sell anything to Iran cause of the western components in the Indian products. Iran might have something to offer for India, but from what I have heard their aerospace industry is in tatters cause of the ban imposed on Iran.
So there we go, was the 11 pages worth of "discussion" really needed.