Okay, now I understand. I'm sorry I've been pressing so hard for clarification, but on a forum like this, where not everyone has the same first language and the members come from a lot of different backgrounds, it's extremely important to be very clear and explicit to avoid asking loaded questions. Because the question, "Would an Islamic Indian subcontinent be better for the region?" implies that you think Hinduism and religious diversity in general, are harmful for the region, which is an entirely subjective opinion that doesn't really fit on a (moderately) serious forum like this. A better way to phrase the question would have been, "How would a fully Islamized India have impacted the history of warfare on the subcontinent?" because when phrased like that, it's clear that you're just curious about the issue and your question isn't coming from any kind of prejudice. Sorry for the rant I suppose, just try to keep in mind how important language is when discussing history/politics/culture.
Anyway now for my two cents I guess are that I doubt a fully Islamic India would do much to stop the numerous ethnic tensions in the country. Even given a fully Islamic population, Iran has a significant number of ethnic conflicts, as does Indonesia (both of which have an overwhelming Muslim majority). Furthermore Europe had unifying Christian institutions for 500 years between 1000-1500 CE and there were numerous wars during that period as well. AFAIK religious institutions have not done much to preclude armed conflicts in history