A mutual defence alliance that only comes into effect based on religion? That would be a first. Certainly quite unique.

And how would it be defined? After all, India itself has the 3rd highest number of Muslims in the world after Indonesia & Pakistan. And the constitution is of a secular character, as is Turkey's. I don't think an alliance on that principle makes a lot of sense. I hope you're joking.
On a more serious note, how would getting involved in wars with countries outside their immediate region of interest supposed to help the collective security of Turkey or Saudi Arabia? For the most part, they have their hands full with adversaries in their immediate periphery. Forcing outside powers to take a more proactive interest in tipping these scales would not be wise IMO (especially for KSA). Let alone the possibility of direct conflict via missiles or other effectors.
Also, how would such an alliance manage escalation responsibility? Supposing an India-Pakistan conflict escalates into a limited (or not so limited) nuclear exchange, would Pakistan's allies also be considered as having a hand in that if they were party to the conflict, thereby have responsibility for the conflict escalating to that level? What would be the response?
This is not a well thought-out paradigm. I really doubt either Saudis or Turks will be interested in becoming an active party to a war against India (or any other out-of-area country, non-Muslim or otherwise). But as I said in my previous post, that remains to be seen.